[NT] Cumulative Security Update for Internet Explorer (MS04-038)

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Date: 10/13/04

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Date: 13 Oct 2004 18:20:45 +0200

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Cumulative Security Update for Internet Explorer (MS04-038)
------------------------------------------------------------------------

SUMMARY

The following advisory provides details on the following vulnerabilities:
CSS Heap Memory Corruption Vulnerability, Similar Method Name Redirection
Cross Domain Vulnerability, Install Engine Vulnerability, Drag and Drop
Vulnerability, Address Bar Spoofing on Double Byte Character Set Systems
Vulnerability, Plug-in Navigation Address Bar Spoofing Vulnerability,
Script in Image Tag File Download Vulnerability, and SSL Caching
Vulnerability.

DETAILS

Affected Software:
Microsoft Windows NT Server 4.0 Service Pack 6a
Microsoft Windows NT Server 4.0 Terminal Server Edition Service Pack 6
Microsoft Windows 2000 Service Pack 3 and Microsoft Windows 2000 Service
Pack 4
Microsoft Windows XP, Microsoft Windows XP Service Pack 1, and Microsoft
Windows XP Service Pack 2
Microsoft Windows XP 64-Bit Edition Service Pack 1
Microsoft Windows XP 64-Bit Edition Version 2003
Microsoft Windows Server 2003
Microsoft Windows Server 2003 64-Bit Edition
Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (Me) Review the FAQ section of this
bulletin for details about these operating systems.

Affected Components:
Internet Explorer 5.01 Service Pack 3 on Windows 2000 SP3:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=2D8E8E97-4946-4994-924B-1FB1DC1881BA&displaylang=en> Download the update.
Internet Explorer 5.01 Service Pack 4 on Windows 2000 SP4:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=72DBE239-AF0A-42B5-B88C-A00371F6EC81&displaylang=en> Download the update.
Internet Explorer 5.5 Service Pack 2 on Microsoft Windows Me:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=BE27F77C-3C2D-45F1-86DF-2B71799DA169&displaylang=en> Download the update.
Internet Explorer 6 on Windows XP:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=A89CFBE8-C299-415D-A9D6-7CC6429C547D&displaylang=en> Download the update.
Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack
3, on Microsoft Windows 2000 Service Pack 4, on Microsoft Windows XP, or
on Microsoft Windows XP Service Pack 1:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=7C1404E6-F5D4-4FED-9573-DD83F2DFF074&displaylang=en> Download the update.
Internet Explorer 6 Service Pack 1 on Microsoft Windows NT Server 4.0
Service Pack 6a, on Microsoft Windows NT Server 4.0 Terminal Service
Edition Service Pack 6, on Microsoft Windows 98, on Microsoft Windows 98
SE, or on Microsoft Windows Me:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=DE8D94C4-7F58-4CE7-B8BD-51CFD795B03E&displaylang=en> Download the update.
Internet Explorer 6 for Windows XP Service Pack 1 (64-Bit Edition):
<http://www.microsoft.com/downloads/details.aspx?FamilyId=C05103E8-4402-4D54-BA03-FBBC24142E4D&displaylang=en> Download the update.
Internet Explorer 6 for Windows Server 2003:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=19E69E5F-9C98-49AD-A61F-4F82A4014412&displaylang=en> Download the update.
Internet Explorer 6 for Windows Server 2003 64-Bit Edition and Windows XP
64-Bit Edition Version 2003:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=566C2A05-2513-4E30-A3EA-87D4BF7F9730&displaylang=en> Download the update.
Internet Explorer 6 for Windows XP Service Pack 2:
<http://www.microsoft.com/downloads/details.aspx?FamilyId=CF47B515-3F51-43E1-9246-2C2264C49E2E&displaylang=en> Download the update.

The following products are not affected by this vulnerability:
Internet Explorer 6 on Windows XP Service Pack 2

Caveats: <http://support.microsoft.com/?id=834707> Microsoft Knowledge
Base Article 834707 documents the currently known issues that customers
may experience when they install this security update. The article also
documents recommended solutions for these issues.

CVE Information:
* Cascading Style Sheets (CSS) Heap Memory Corruption Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0842>
CAN-2004-0842
* Similar Method Name Redirection Cross Domain Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0727>
CAN-2004-0727
* Install Engine Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0216>
CAN-2004-0216
* Drag and Drop Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0839>
CAN-2004-0839
* Address Bar Spoofing on Double Byte Character Set Locale Vulnerability
- <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0844>
CAN-2004-0844
* Plug-in Navigation Address Bar Spoofing Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0843>
CAN-2004-0843
* Script in Image Tag File Download Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0841>
CAN-2004-0841
* SSL Caching Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0845>
CAN-2004-0845

Mitigating Factors for CSS Heap Memory Corruption Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site. After they click the link, they would be prompted to
perform several actions. An attack could only occur after they performed
these actions.
* An attacker who successfully exploited this vulnerability could gain
the same privileges as the user. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been installed. Outlook Express 5.5 Service
Pack 2 opens HTML e-mail in the Restricted sites zone if Microsoft
Security Bulletin <http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018
has been installed. The Restricted sites zone helps reduce attacks that
could attempt to exploit this vulnerability.
The risk of attack from the HTML e-mail vector can be significantly
reduced if you meet all the following conditions:
* Install the update that is included with Microsoft Security Bulletin
<http://www.microsoft.com/technet/security/bulletin/MS03-040.mspx>
MS03-040 or a later Cumulative Security Update for Internet Explorer.
* Use Outlook Express 5.5 Service Pack 2 or later and have applied the
update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 or a later
Cumulative Security Update for Outlook Express.
* Use Microsoft Outlook 98 and Outlook 2000 with the Microsoft Outlook
E-mail Security Update installed
* Use Microsoft Outlook Express 6 or later or Microsoft Outlook 2000
Service Pack 2 or later in their default configuration.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode mitigates this vulnerability. See the FAQ section for this security
update for more information about Internet Explorer Enhanced Security
Configuration.

Workarounds for CSS Heap Memory Corruption Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.
Set Internet and Local Intranet security zone settings to High to prompt
before running ActiveX control and Active scripting in the Internet zone
and in the Local Intranet zone.
You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls and Active scripting. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and click Custom Level.
4. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
5. Under Active Scripting in the Scripting section, click Prompt, and then
click OK.
6. Click Local intranet, and then click Custom Level.
7. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
8. Under Active Scripting in the Scripting section, , click Prompt.
9. Click OK two times to return to Internet Explorer.

Impact of Workaround: There are side effects to prompting before running
ActiveX controls. Many Web sites that are on the Internet or on an
intranet use ActiveX to provide additional functionality. For example, an
online e-commerce site or banking site may use ActiveX controls to provide
menus, ordering forms, or even account statements. Prompting before
running ActiveX controls is a global setting that affects all Internet and
intranet sites. You will be prompted frequently when you enable this
workaround. For each prompt, if you feel you trust the site that you are
visiting, click Yesto run ActiveX controls. If you do not want to be
prompted for all these sites, use the "Restrict Web sites to only your
trusted Web sites" workaround.

Restrict Web sites to only your trusted Web sites:
After you set Internet Explorer to require a prompt before it runs ActiveX
controls and active scripting in the Internet zone and in the Local
Intranet zone, you can add sites that you trust to Internet Explorer's
Trusted sites zone. This will allow you to continue to use trusted Web
sites exactly as you do today, while helping to protect you from this
attack on untrusted sites. Microsoft recommends that you only add sites
that you trust to the Trusted sites zone.

To do this follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then
click the Security tab.
2. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel,
click to clear the Require server verification (https:) for all sites in
this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone
6. Click OK two times to accept the changes and return to Internet
Explorer.

Add any sites that you trust not to take malicious action on your
computer. One in particular that you may want to add is
"*.windowsupdate.microsoft.com" (without the quotes). This is the site
that will host the update, and it requires the use of an ActiveX control
to install the update.

Install the
<http://www.microsoft.com/office/previous/outlook/2002security.asp>
Outlook E-mail Security Update if you are using Outlook 2000 SP1 or
earlier:
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
Outlook E-mail Security Update has been applied.
Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.

Install the update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 if you are using
Outlook Express 5.5 SP2:
Outlook Express 5.5 Service Pack 2 opens HTML e-mail in the Restricted
sites zone if the update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.
Read e-mail messages in plain text format if you are using Outlook 2002 or
later, or Outlook Express 6 SP1 or later, to help protect yourself from
the HTML e-mail attack vector:
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or
later and Microsoft Outlook Express 6 users who have applied Internet
Explorer 6 Service Pack 1 can enable this setting and view e-mail messages
that are not digitally signed or e-mail messages that are not encrypted in
plain text only.
Digitally signed e-mail messages or encrypted e-mail messages are not
affected by the setting and may be read in their original formats. For
more information about enabling this setting in Outlook 2002, see
Microsoft Knowledge Base Article
<http://support.microsoft.com/default.aspx?scid=kb;en-us;307594> 307594.
For information about this setting in Outlook Express 6, see Microsoft
Knowledge Base Article <http://support.microsoft.com/?kbid=291387>
291387.
Impact of Workaround: E-mail messages that are viewed in plain text format
will not contain pictures, specialized fonts, animations, or other rich
content. In addition:
The changes are applied to the preview pane and to open messages.
Pictures become attachments so that they are not lost.
Because the message is still in Rich Text or HTML format in the store, the
object model (custom code solutions) may behave unexpectedly.

FAQ for CSS Heap Memory Corruption Vulnerability:
What is the scope of the vulnerability?
This is a buffer overrun vulnerability. If a user is logged on with
administrative privileges, an attacker who successfully exploited this
vulnerability could take complete control of an affected system, including
installing programs; viewing, changing, or deleting data; or creating new
accounts that have full privileges. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.

What causes the vulnerability?
An unchecked buffer in Internet Explorer processing of CSS.

What are CSS?
Cascading Style Sheets (CSS) is a technology that allows Web authors to
have increased control of the design and interaction of their Web pages.
For more information about CSS, visit this
<http://msdn.microsoft.com/library/default.asp?url=/workshop/author/css/css_node_entry.asp> Microsoft Developer Network (MSDN) Web site.

How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by creating a malicious Web
page or an HTML e-mail message and then persuading the user to visit the
page or to view the HTML e-mail message. When the user visited the page or
viewed the e-mail message, the attacker could access information from
other Web sites, access local files on the system, or cause malicious code
to run in the security context of the locally logged on user.

What systems are primarily at risk from the vulnerability?
This vulnerability requires a user to be logged on and to be reading
e-mail or visiting Web sites for any malicious action to occur. Therefore,
any systems where e-mail is read or where Internet Explorer is used
frequently, such as users workstations or terminal servers, are at the
most risk from this vulnerability. Systems that are not typically used to
read e-mail or to visit Web sites, such as most server systems, are at a
reduced risk.

Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition
critically affected by this vulnerability?
Yes. Windows 98, Windows 98 Second Edition, and Windows Millennium Edition
are critically affected by this vulnerability. Critical security updates
for these platforms may not be available concurrently with the other
security updates that are provided as part of this security bulletin. They
will be made available as soon as possible following the release. When
these security updates are available, you will be able to download them
only from the <http://go.microsoft.com/fwlink/?LinkId=21130> Windows
Update Web site. For more information about severity ratings, visit this
<http://go.microsoft.com/fwlink/?LinkId=21140> Microsoft Web site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates the length of a message while processing CSS.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
Yes. This vulnerability has been publicly disclosed. It has been assigned
Common Vulnerability and Exposure number CAN-2004-0842.

When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
No. Microsoft had not received any information indicating that this
vulnerability had been publicly used to attack customers and had not seen
any examples of proof of concept code published when this security
bulletin was originally issued.

Mitigating Factors for Similar Method Name Redirection Cross Domain
Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site.
* An attacker who successfully exploited this vulnerability could gain
the same privileges as the user. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.
* Customers who have installed both the update referenced in Microsoft
Security Bulletin <http://go.microsoft.com/fwlink/?LinkId=30585> MS04-024
and have installed the ADODB.Stream update that is referenced in Knowledge
Base Article <http://support.microsoft.com/?id=870669> 870669 will be at
a reduced risk of this vulnerability resulting in remote code execution.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been installed. Outlook Express 5.5 Service
Pack 2 opens HTML e-mail in the Restricted sites zone if Microsoft
Security Bulletin <http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018
has been installed. The Restricted sites zone helps reduce attacks that
could attempt to exploit this vulnerability.
* The risk of attack from the HTML e-mail vector can be significantly
reduced if you meet all the following conditions:
* Install the update that is included with Microsoft Security Bulletin
<http://www.microsoft.com/technet/security/bulletin/MS03-040.mspx>
MS03-040 or a later Cumulative Security Update for Internet Explorer.
* Use Outlook Express 5.5 Service Pack 2 or later and have applied the
update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 or a later
Cumulative Security Update for Outlook Express.
* Use Microsoft Outlook 98 and Outlook 2000 with the Microsoft Outlook
E-mail Security Update installed
* Use Microsoft Outlook Express 6 or later or Microsoft Outlook 2000
Service Pack 2 or later in their default configuration.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration that
mitigates this vulnerability. See the FAQ section for this security update
for more information about Internet Explorer Enhanced Security
Configuration.

Workarounds for Similar Method Name Redirection Cross Domain
Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.
Set Internet and Local Intranet security zone settings to High to prompt
before running ActiveX controls and Active scripting in the Internet zone
and in the Local Intranet zone:

You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls and Active scripting. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
5. Under Active Scripting in the Scripting section, click Prompt, and then
click OK.
6. Click Local intranet, and then click Custom Level.
7. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
8. Under Active Scripting in the Scripting section, click Prompt.
9. Click OK two times to return to Internet Explorer.

Prompting before running ActiveX controls is a global setting that affects
all Internet and intranet sites. You will be prompted frequently when you
enable this workaround. For each prompt, if you trust the site that you
are visiting, click Yesto run ActiveX controls. If you do not want to be
prompted for all these sites, use the "Restrict Web sites to only your
trusted Web sites" workaround.

To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
4. If you want to add sites that do not require an encrypted channel,
click to clear the Require server verification (https:) for all sites in
this zone check box.
5. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
6. Repeat these steps for each site that you want to add to the zone
7. Click OK two times to accept the changes and to return to Internet
Explorer.

Add any sites that you trust not to take malicious action on your
computer. You may want to add "*.windowsupdate.microsoft.com" (without the
quotation marks) to your Trusted Sites zone. This site hosts the update.
This site uses an ActiveX control to install the update.

Strengthen the security settings for the Local Machine zone in Internet
Explorer:
Because this vulnerability permits an attacker to run HTML code in the
Local Machine security zone, users can reduce the impact of this
vulnerability by restricting the default settings in this zone. For more
information about these settings, and for more information about the
potential impacts of changing these default settings, see Microsoft
Knowledge Base Article <http://support.microsoft.com/?id=833633> 833633.

Impact of Workaround: Microsoft recommends that customers consider these
changes to Internet Explorer security settings as a last resort only. If
you make these changes, you may lose some functionality for some Windows
programs and components. Before you make these changes in a production
environment, test the changes extensively to verify that mission-critical
programs continue to work correctly for all users.

Install the
<http://www.microsoft.com/office/previous/outlook/2002security.asp>
Outlook E-mail Security Update if you are using Outlook 2000 SP1 or
earlier:
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/previous/outlook/2002security.asp>
Outlook E-mail Security Update has been applied.

Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.

Install the update that is included with Microsoft Security Bulletin
MS04-018 if you are using Outlook Express 5.5 SP2:
Outlook Express 5.5 Service Pack 2 opens HTML e-mail in the Restricted
sites zone if the update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.

Impact of Workaround: E-mail messages that are viewed in plain text format
will not contain pictures, specialized fonts, animations, or other rich
content. In addition:
* The changes are applied to the preview pane and to open messages.
* Pictures become attachments so that they are not lost.
* Because the message is still in Rich Text or HTML format in the store,
the object model (custom code solutions) may behave unexpectedly.

FAQ for Similar Method Name Redirection Cross Domain Vulnerability:
What is the scope of the vulnerability?
A vulnerability in the cross domain security model exists in Internet
Explorer because of the way that it handles navigation methods by
functions that have similar names. An attacker could exploit the
vulnerability by constructing a malicious Web page that could potentially
allow remote code execution if a user visited a malicious Web site. An
attacker who successfully exploited this vulnerability could run malicious
script code in the Local Machine security zone in Internet Explorer or
access information in a different domain. In the worst case, if a user is
logged on with administrative privileges, an attacker who successfully
exploited this vulnerability could take complete control of an affected
system. Users whose accounts are configured to have fewer privileges on
the system would be at less risk than users who operate with
administrative privileges.

What causes the vulnerability?
The process that the Internet Explorer cross-domain security model uses to
validate navigation methods that have similar function names.

What is the cross-domain security model that Internet Explorer uses?
One of the principal security functions of a browser is to make sure that
browser windows that are under the control of different Web sites cannot
interfere with each other or access each other's data, while allowing
windows from the same site to interact with each other. To differentiate
between cooperative and uncooperative browser windows, the concept of a
"domain" has been created. A domain is a security boundary - any open
windows within the same domain can interact with each other, but windows
from different domains cannot. The cross-domain security model is the part
of the security architecture that keeps windows from different domains
from interfering with each other.

The simplest example of a domain is associated with Web sites. If you
visit http://www.wingtiptoys.com, and it opens a window to
http://www.wingtiptoys.com/security, the two windows can interact with
each other because both sites belong to the same domain,
http://www.wingtiptoys.com. However, if you visited
http://www.wingtiptoys.com, and it opened a window to a different Web
site, the cross-domain security model would protect the two windows from
each other. The concept goes even further. The file system on your local
computer is also a domain. For example, http://www.wingtiptoys.com could
open a window and show you a file on your hard disk. However, because your
local file system is in a different domain from the Web site, the
cross-domain security model should prevent the Web site from reading the
file that is being displayed.

The Internet Explorer cross-domain security model can be configured by
using the security zone settings in Internet Explorer.

What are Internet Explorer security zones?
Internet Explorer security zones are part of a system that divides online
content into categories or zones that are based on the trustworthiness of
the content. Specific Web domains can be assigned to a zone, depending on
how much trust is placed in the content of each domain. The zone then
restricts the capabilities of the Web content, based on the zone's policy.
By default, most Internet domains are treated as part of the Internet
zone. By default, the policy of the Internet zone prevents scripts and
other active code from accessing resources on the local system.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run
malicious script code in the Local Machine security zone in Internet
Explorer. This could allow an attacker to take complete control of the
affected system.

How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by creating a malicious Web
page or an HTML e-mail message and then convincing the user to visit this
page or to view the HTML e-mail message. When the user visited the page or
viewed the e-mail message, the attacker could access information from
other Web sites, access local files on the system, or cause script to run
in the security context of the Local Machine security zone.

Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition
critically affected by this vulnerability?
Yes. Windows 98, Windows 98 Second Edition, and Windows Millennium Edition
are critically affected by this vulnerability. Critical security updates
for these platforms may not be available concurrently with the other
security updates provided as part of this security bulletin. They will be
made available as soon as possible following the release. When these
security updates are available, you will be able to download them only
from the <http://go.microsoft.com/fwlink/?LinkId=21130> Windows Update
Web site. For more information about severity ratings, visit this
<http://go.microsoft.com/fwlink/?LinkId=21140> Microsoft Web site.

Could the vulnerability be exploited over the Internet?
Yes. An attacker may be able to exploit this vulnerability over the
Internet. Microsoft has provided information on how you can help protect
your PC. End users can visit the Protect Your PC Web site. IT
Professionals can visit the Security Guidance Center Web site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates navigation methods by functions that have similar
names.

When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
Yes. When the security bulletin was released, Microsoft had received
information that this vulnerability was being exploited.

Does installing this security update help protect customers from the code
that has been published publicly that attempts to exploit this
vulnerability?
Yes. This security update addresses the vulnerability that is currently
being exploited. The vulnerability that has been addressed has been
assigned the Common Vulnerability and Exposure number CAN-2004-0727.

Mitigating Factors for Install Engine Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site.
* An attacker who successfully exploited this vulnerability could gain
the same privileges as the user. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
Microsoft
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been applied. Outlook Express 5.5 Service Pack
2 opens HTML e-mail in the Restricted sites zone if the update that is
included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
The Restricted sites zone helps reduce attacks that could attempt to
exploit this vulnerability.
* The risk of attack from the HTML e-mail vector can be significantly
reduced if you meet all the following conditions:
* Install the update that is included with Microsoft Security Bulletin
<http://www.microsoft.com/technet/security/bulletin/MS03-040.mspx>
MS03-040 or a later Cumulative Security Update for Internet Explorer.
* Use Outlook Express 5.5 Service Pack 2 or later and have applied the
update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 or a later
Cumulative Security Update for Outlook Express.
* Use Microsoft Outlook 98 and Outlook 2000 with the Microsoft
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update applied.
* Use Microsoft Outlook Express 6 or later or Microsoft Outlook 2000
Service Pack 2 or later in their default configuration.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration that
mitigates this vulnerability. See the FAQ section for this security update
for more information about Internet Explorer Enhanced Security
Configuration.

Workarounds for Install Engine Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.

Set Internet and Local Intranet security zone settings to High to prompt
before running ActiveX controls and Active scripting in the Internet zone
and in the Local Intranet zone:
You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls and Active scripting. To do this, follow these steps:

1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
5. Under Active Scripting in the Scripting section, click Prompt, and then
click OK.
6. Click Local intranet, and then click Custom Level.
7. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
8. Under Active Scripting in the Scripting section, click Prompt.
9. Click OK two times to return to Internet Explorer.

Restrict Web sites to only your trusted Web sites:
After you set Internet Explorer to require a prompt before it runs ActiveX
controls and Active scripting in the Internet zone and in the Local
Intranet zone, you can add sites that you trust to Internet Explorer's
Trusted sites zone. If you do this, you can continue to use trusted Web
sites exactly as you do today, while helping to protect you from this
attack on untrusted sites. We recommend that you add only sites that you
trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
4. If you want to add sites that do not require an encrypted channel,
click to clear the Require server verification (https:) for all sites in
this zone check box.
5. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
6. Repeat these steps for each site that you want to add to the zone
7. Click OK two times to accept the changes and to return to Internet
Explorer.

Install the
<http://www.microsoft.com/office/previous/outlook/2002security.asp>
Outlook E-mail Security Update if you are using Outlook 2000 SP1 or
earlier:
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been applied.

Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.

Install the update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 if you are using
Outlook Express 5.5 SP2.
Outlook Express 5.5 Service Pack 2 opens HTML e-mail in the Restricted
sites zone if the update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.
Read e-mail messages in plain text format if you are using Outlook 2002 or
later, or Outlook Express 6 SP1 or later, to help protect yourself from
the HTML e-mail attack vector.
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or
later and Microsoft Outlook Express 6 users who have applied Internet
Explorer 6 Service Pack 1 can enable this setting and view e-mail messages
that are not digitally signed or e-mail messages that are not encrypted in
plain text only.
Digitally signed e-mail messages or encrypted e-mail messages are not
affected by the setting and may be read in their original formats. For
more information about enabling this setting in Outlook 2002, see
Microsoft Knowledge Base Article
<http://support.microsoft.com/?id=307594> 307594.
For information about this setting in Outlook Express 6, see Microsoft
Knowledge Base Article <http://support.microsoft.com/?id=291387> 291387.
Impact of Workaround: E-mail messages that are viewed in plain text format
will not contain pictures, specialized fonts, animations, or other rich
content. In addition:
* The changes are applied to the preview pane and to open messages.
* Pictures become attachments so that they are not lost.
* Because the message is still in Rich Text or HTML format in the store,
the object model (custom code solutions) may behave unexpectedly.

FAQ for Install Engine Vulnerability:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. If a user is logged on with
administrative privileges, an attacker who successfully exploited the most
severe of these vulnerabilities could take complete control of an affected
system, including installing programs; viewing, changing, or deleting
data; or creating new accounts with full privileges. Users whose accounts
are configured to have fewer privileges on the system would be at less
risk than users who operate with administrative privileges.

What causes the vulnerability?
An unchecked buffer in the Internet Explorer Install Engine.

What is the Install Engine?
The Install Engine is part of the Internet Explorer Active Setup
technology. Active Setup allows an installation program to receive
additional files from the Internet that are needed for program
initialization.

How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by creating a malicious Web
page or an HTML e-mail message and then enticing the user to visit this
page or to view the HTML e-mail message. When the user visited the page or
viewed the e-mail message, the attacker could access information from
other websites, local files on the system, or cause malicious code to run
in the security context of the locally logged on user.

Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition
critically affected by this vulnerability?
Yes. Windows 98, Windows 98 Second Edition, and Windows Millennium Edition
are critically affected by this vulnerability. Critical security updates
for these platforms may not be available concurrently with the other
security updates provided as part of this security bulletin. They will be
made available as soon as possible following the release. When these
security updates are available, you will be able to download them only
from the <http://go.microsoft.com/fwlink/?LinkId=21130> Windows Update
Web site. For more information about severity ratings, visit this
<http://go.microsoft.com/fwlink/?LinkId=21140> Microsoft Web site.

What does the update do?
The update removes the vulnerability by modifying the way that the Install
Engine in Internet Explorer validates the length of a message before it
passes the message to the allocated buffer.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.

Mitigating Factors for Drag and Drop Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site. After they click the link, they would need to perform an
action on the malicious web site that would invoke drag-and-drop handling
in Internet Explorer.
* This vulnerability allows an attacker to place malicious code on the
user's system in specified locations. An attack could only occur after the
user ran this code, either by restarting the system, by logging off and
then logging back on to the system, or by inadvertently running the code
that the attacker saved locally on the system.
* An attacker who successfully exploited this vulnerability could gain
the same privileges as the user. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been applied. Outlook Express 5.5 Service Pack
2 opens HTML e-mail in the Restricted sites zone if the update that is
included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
The Restricted sites zone helps reduce attacks that could try to exploit
this vulnerability.
* The risk of attack from the HTML e-mail vector can be significantly
reduced if you meet all the following conditions:
* Install the update that is included with Microsoft Security Bulletin
<http://www.microsoft.com/technet/security/bulletin/MS03-040.mspx>
MS03-040 or a later Cumulative Security Update for Internet Explorer.
* Use Outlook Express 5.5 Service Pack 2 or later and have applied the
update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 or a later
Cumulative Security Update for Outlook Express.
* Use Microsoft Outlook 98 and Outlook 2000 with the Microsoft
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update applied.
* Use Microsoft Outlook Express 6 or later or Microsoft Outlook 2000
Service Pack 2 or later in their default configuration.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode mitigates this vulnerability. See the FAQ section for this
vulnerability for more information about Internet Explorer Enhanced
Security Configuration.

Workarounds for Drag and Drop Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.
Set Internet and Local Intranet security zone settings to "High" to prompt
before running ActiveX controls and Active scripting in the Internet zone
and in the Local Intranet zone:
You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls and Active scripting. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
5. Under Active Scripting in the Scripting section, click Prompt, and then
click OK.
6. Click Local intranet, and then click Custom Level.
7. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
8. Under Active Scripting in the Scripting section, click Prompt.
9. Click OK two times to return to Internet Explorer.

Install the Outlook E-mail Security Update if you are using Outlook 2000
SP1 or earlier:
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
Outlook E-mail Security Update has been applied.
Customers who use any of these products could be at a reduced risk from an
e-mail-borne attack that tries to exploit this vulnerability unless the
user clicks a malicious link in the e-mail message.

Read e-mail messages in plain text format if you are using Outlook 2002 or
later, or Outlook Express 6 SP1 or later, to help protect yourself from
the HTML e-mail attack vector:
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or
later and Microsoft Outlook Express 6 users who have applied Internet
Explorer 6 Service Pack 1 can enable this setting and view e-mail messages
that are not digitally signed or e-mail messages that are not encrypted in
plain text only.
Digitally signed e-mail messages or encrypted e-mail messages are not
affected by the setting and may be read in their original formats. For
more information about enabling this setting in Outlook 2002, see
Microsoft Knowledge Base Article
<http://support.microsoft.com/?id=307594> 307594.
For information about this setting in Outlook Express 6, see Microsoft
Knowledge Base Article <http://support.microsoft.com/?id=291387> 291387.
<Impact of Workaround:> Impact of Workaround: E-mail messages that are
viewed in plain text format will not contain pictures, specialized fonts,
animations, or other rich content. In addition:
* The changes are applied to the preview pane and to open messages.
* Pictures become attachments so that they are not lost.
* Because the message is still in Rich Text or HTML format in the store,
the object model (custom code solutions) may behave unexpectedly.

FAQ for Drag and Drop Vulnerability:
What is the scope of the vulnerability?
This vulnerability involves Drag and Drop events in Internet Explorer and
could result in an executable file being saved on the user's system. The
user would not receive a dialog box requesting to approve the download. To
exploit this vulnerability, an attacker would have to host a malicious Web
site that contained a Web page that was designed to exploit this
vulnerability and then persuade a user to visit that site. If the user
took certain actions on that Web page, code of the attacker's choice could
be saved in specified locations on the user's system.

What causes the vulnerability?
This vulnerability is caused by Drag and Drop technology improperly
validating some Dynamic HTML (DHTML) events. This vulnerability permits a
file to be downloaded to the user's system after the user clicks a link.

What are DHMTL Events?
DHTML events are special actions that are provided by the DHTML Object
Model. These events can be used in script code to add dynamic content to a
Web site. For more information about DHTML events, visit this
<http://msdn.microsoft.com/workshop/author/dhtml/reference/events.asp>
MSDN Web site.

How could an attacker exploit the vulnerability?
An attacker who successfully exploited this vulnerability could save code
of their choice to the user's local file system. Although this code could
not be run through this vulnerability directly, the operating system might
open the file if it is saved to a sensitive location, or a user may
activate the file inadvertently and cause the attacker's code to run.

Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition
critically affected by this vulnerability?
No. Although Windows 98, Windows 98 Second Edition, and Windows Millennium
Edition do contain the affected component, the vulnerability is not
critical. For more information about severity ratings, visit this
<http://go.microsoft.com/fwlink/?LinkId=21140> Microsoft Web site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates some Drag and Drop events.

Mitigating Factors for Address Bar Spoofing on Double Byte Character Set
Systems Vulnerability:
This vulnerability only affects systems that are utilizing Double Byte
Character Sets. These character sets are used on some Asian versions of
Microsoft Windows and can be set using the system locale.
In a Web-based attack scenario, an attacker would have to host a Web site
that contains a Web page that is used to exploit this vulnerability. An
attacker would have no way to force users to visit a malicious Web site.
Instead, an attacker would have to persuade them to visit the Web site,
typically by getting them to click a link that takes them to the
attacker's site.
The following products are not affected by this vulnerability:
* Internet Explorer 6 on Microsoft Windows XP Service Pack 2
* Internet Explore 6.0
* Internet Explorer 5.5 Service Pack 2
* Internet Explorer 5.01 Service Pack 4
* Internet Explorer 5.01 Service Pack 3

FAQ for Address Bar Spoofing on Double Byte Character Set Systems
Vulnerability:
What is the scope of the vulnerability?
This is a spoofing vulnerability. It affects the Address bar that Internet
Explorer uses to display the currently visited Web site. This
vulnerability could result in an incorrect URL being listed in the Address
bar that is not the actual Web page that is appearing in Internet
Explorer. For example, an attacker could create a link that would display
http://www.tailspintoys.com in the Address bar when the user clicked the
link. However, Internet Explorer would actually display content from
another Web site, such as http://www.wingtiptoys.com.

What causes the vulnerability?
This vulnerability is caused by a canonicalization error that occurs when
Internet Explorer parses special characters in a HTTP URL on Double Byte
Character Set systems.

What are Double Byte Character Sets?
Double Byte Character Sets (DBCS) are an expanded 8-bit character set
where the smallest unit is a byte. Some characters in a DBCS have a single
byte code value and some have a double byte code value. A DBCS can be
thought of as the ANSI character set for some Asian versions of Microsoft
Windows. More information on DBCS can be found on the Double-byte
Character Sets page on MSDN.

How do I know if I am running a DBCS locale?
DBCS can be thought of as the ANSI character set for some Asian versions
of Microsoft Windows. Typically these are limited to Chinese, Japanese,
and Korean languages. For more information on system locales and
determining the system locale please visit this
<http://www.microsoft.com/globaldev/DrIntl/faqs/Locales.mspx> Microsoft
Web site.

How could an attacker exploit the vulnerability?
An attacker could use this vulnerability to create a Web page that would
display a URL of the attacker's choosing in the Address bar, while
displaying a different Web site in the browser window. An attacker could
use this vulnerability to create a malicious page that spoofs a legitimate
site. For example, an attacker could create a Web page that looks like a
user's online e-mail site. However, this Web page would be hosted on a
malicious Web site. An attacker could use this vulnerability to display a
legitimate looking URL in the Address bar. A user might see this URL and
mistakenly provide sensitive information to the attacker's site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates URLs on DBCS locales.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
Microsoft had not received any information indicating that this
vulnerability had been publicly disclosed when this security bulletin was
originally issued.

Mitigating Factors for Plug-in Navigation Address Bar Spoofing
Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration that
mitigates this vulnerability. See the FAQ section for this security update
for more information about Internet Explorer Enhanced Security
Configuration.
The following products are not affected by this vulnerability.
* Internet Explorer 5.01 Service Pack 4
* Internet Explorer 5.01 Service Pack 3

Workarounds for Plug-in Navigation Address Bar Spoofing Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.
Set Internet and Local Intranet security zone settings to High to prompt
before running ActiveX controls and Active scripting in the Internet zone
and in the Local Intranet zone:
You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls and Active scripting. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
5. Under Active Scripting in the Scripting section, click Prompt, and then
click OK.
6. Click Local intranet, and then click Custom Level.
7. Under Run ActiveX controls and plug-ins in the ActiveX controls and
plug-ins section, click Prompt.
8. Under Active Scripting in the Scripting section, click Prompt.
9. Click OK two times to return to Internet Explorer.

Restrict Web sites to only your trusted Web sites
After you set Internet Explorer to require a prompt before it runs ActiveX
controls and Active scripting in the Internet zone and in the Local
Intranet zone, you can add sites that you trust to Internet Explorer's
Trusted sites zone. If you do this, you can continue to use trusted Web
sites exactly as you do today, while helping to protect you from this
attack on untrusted sites. We recommend that you add only sites that you
trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
4. If you want to add sites that do not require an encrypted channel,
click to clear the Require server verification (https:) for all sites in
this zone check box.
5. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
6. Repeat these steps for each site that you want to add to the zone
7.Click OK two times to accept the changes and to return to Internet
Explorer.

FAQ for Plug-in Navigation Address Bar Spoofing Vulnerability:
What is the scope of the vulnerability?
This is a spoofing vulnerability. It affects the Address bar that Internet
Explorer uses to display the currently visited Web site. This
vulnerability could result in an incorrect URL being listed in the Address
bar that is not the actual Web page that is appearing in Internet
Explorer. For example, an attacker could create a link that would display
http://www.tailspintoys.com in the Address bar when the user clicked the
link. However, Internet Explorer would actually display content from
another Web site, such as http://www.wingtiptoys.com.

What causes the vulnerability?
The way that Internet Explorer handles navigations from plug-ins.

What are plug-ins?
Plug-ins are third-party components that extend the features of Internet
Explorer. Examples of plug-ins include ActiveX controls.

How could an attacker exploit the vulnerability?
An attacker could use this vulnerability to create a Web page that hosts a
plug-in that could make Internet Explorer display a URL of the attacker's
choosing in the Address bar, while displaying a different Web site in the
browser window. An attacker could use this vulnerability to create a
malicious page that spoofs a legitimate site. For example, an attacker
could create a Web page that looks like a user's online e-mail site.
However, this Web page would be hosted on a malicious Web site. An
attacker could use this vulnerability to display a legitimate looking URL
in the Address bar. A user might see this URL and mistakenly provide
sensitive information to the attacker's site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates plug-in navigations.

Mitigating Factors for Script in Image Tag File Download Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's site. After they click the link, they would need to perform an
action on the malicious Web site, such as clicking an image.
* This vulnerability allows an attacker to put malicious code on the user
s system in specified locations. An attack could occur only after the user
ran this code, either by restarting the system, by logging off and then
logging back on to the system, or by inadvertently running the code that
the attacker has saved locally on the system.
* An attacker who successfully exploited this vulnerability could gain
the same privileges as the user. Users whose accounts are configured to
have fewer privileges on the system would be at less risk than users who
operate with administrative privileges.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and
Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
<http://www.microsoft.com/office/outlook/evaluation/security.asp> Outlook
E-mail Security Update has been applied. Outlook Express 5.5 Service Pack
2 opens HTML e-mail in the Restricted sites zone if the update that is
included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been applied.
The Restricted sites zone helps reduce attacks that could try to exploit
this vulnerability.
The risk of attack from the HTML e-mail vector can be significantly
reduced if you meet all the following conditions:
* Install the update that is included with Microsoft Security Bulletin
<http://www.microsoft.com/technet/security/bulletin/MS03-040.mspx>
MS03-040 or a later Cumulative Security Update for Internet Explorer.
* Use Outlook Express 5.5 Service Pack 2 or later and have applied the
update that is included with Microsoft Security Bulletin
<http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 or a later
Cumulative Security Update for Outlook Express.
* Use Microsoft Outlook 98 and Outlook 2000 with the
<http://www.microsoft.com/office/outlook/evaluation/security.asp>
Microsoft Outlook E-mail Security Update applied.
* Use Microsoft Outlook Express 6 or later or Microsoft Outlook 2000
Service Pack 2 or later in the default configuration.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode mitigates this vulnerability. See the FAQ section for this
vulnerability for more information about Internet Explorer Enhanced
Security Configuration.

Mitigating Factors for SSL Caching Vulnerability:
* An attacker would have to host a Web site that contains a Web page that
is used to exploit this vulnerability. An attacker would have no way to
force users to visit a malicious Web site. Instead, an attacker would have
to persuade them to visit the Web site, typically by getting them to click
a link that takes them to the attacker's site.
* Before the user visits the legitimate SSL protected Web site, an
attacker would have to redirect the user s navigation from the legitimate
Web site to their malicious Web site that has the same host name. To do
this, the attacker would have to intercept network traffic or point the
user s system to a malicious DNS server.

Workarounds for SSL Caching Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
below.
Set advanced security settings to not saved encrypted pages to disk:
You can help protect against these vulnerabilities by changing your
settings to not save encrypted contents to disk. To do this, follow these
steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Advanced tab.
3. Under Settings, scroll to Security.
4. Under Settings, in the Security section, click Do not save encrypted
pages to disk.
5. Click OK two times to return to Internet Explorer.

FAQ for SSL Caching Vulnerability:
What is the scope of the vulnerability?
This is an information disclosure and spoofing vulnerability. An attacker
who successfully exploited this vulnerability could gain access to
information or spoof content on SSL protected Web sites.

What causes the vulnerability?
Internet Explorer s handling of cached SSL contents.

What is SSL?
<http://www.ietf.org/rfc/rfc2246.txt> Secure Sockets Layer (SSL) is a
protocol that allows web sessions to be encrypted for greater security. In
Internet Explorer, when you visit a Web site and a yellow lock icon
appears in the lower right corner of the browser window, the current
session is protected by SSL.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could access
information or spoof content on Web sites that are protected by SSL.

How could an attacker exploit the vulnerability?
An attacker could exploit the vulnerability by creating a Web site that
has the same host name as a legitimate SSL protected Web site. If the
attacker were then able to redirect navigation from the legitimate Web
Site at that address to their malicious Web site, items of the attacker s
choosing could be cached to the local system.
When the user visited the legitimate site in a second session, these items
would be loaded in the context of the legitimate Web site. These items
could include script code, images, or other locally cached content. This
content could be crafted to obtain sensitive information that would
typically be protected by SSL security.

What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates content during SSL sessions.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. We received information about this vulnerability through responsible
disclosure.

ADDITIONAL INFORMATION

The information has been provided by Microsoft Product Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/MS04-038.mspx>
http://www.microsoft.com/technet/security/bulletin/MS04-038.mspx

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