[NT] Cumulative Security Update for Internet Explorer (MS06-067)
- From: SecuriTeam <support@xxxxxxxxxxxxxx>
- Date: 15 Nov 2006 10:37:32 +0200
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Cumulative Security Update for Internet Explorer (MS06-067)
------------------------------------------------------------------------
SUMMARY
This update resolves several newly discovered, publicly and privately
reported vulnerabilities. If a user is logged on with administrative user
rights, an attacker who successfully exploited the most severe of these
vulnerabilities could take complete control of an affected system. An
attacker could then install programs; view, change, or delete data; or
create new accounts with full user rights. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.
DETAILS
Affected Software:
* Microsoft Windows 2000 Service Pack 4
* Microsoft Windows XP Service Pack 2
* Microsoft Windows XP Professional x64 Edition
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with SP1 for Itanium-based Systems
* Microsoft Windows Server 2003 x64 Edition
Non-Affected Software:
* Windows Vista
Affected Components:
Microsoft Internet Explorer 5.01 Service Pack 4 on Windows 2000 Service
Pack 4 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B743B081-20D4-4C1C-BC86-254D2F653953> Download the update
Microsoft Internet Explorer 6 Service Pack 1 on Windows 2000 Service Pack
4 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=C65C8EE7-F78D-4D52-A20C-1F896E0DC0A8> Download the update
Microsoft Internet Explorer 6 for Windows XP Service Pack 2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=EA3CE61C-3A28-4777-9EEF-1486BB483C4F> Download the update
Microsoft Internet Explorer 6 for Windows XP Professional x64 Edition -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=C535A36F-705E-4663-9EE4-B82632A50F0A> Download the update
Microsoft Internet Explorer 6 for Windows Server 2003 and Microsoft
Windows Server 2003 Service Pack 1 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=35EEF49C-E3D7-41EE-82F5-964A3959D453> Download the update
Microsoft Internet Explorer 6 for Windows Server 2003 for Itanium-based
Systems and Windows Server 2003 with SP1 for Itanium-based Systems -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=E8E03176-F93B-4DE7-AC95-01F9B1C5409C> Download the update
Microsoft Internet Explorer 6 for Windows Server 2003 x64 Edition -
<http://www.microsoft.com/downloads/details.aspx?familyid=ABE4FE3E-BDB6-44B1-B203-528C67980B8F> Download the update
Non-Affected Components:
* Windows Internet Explorer 7 for Windows XP Service Pack 2
* Windows Internet Explorer 7 for Windows XP Professional x64 Edition
* Windows Internet Explorer 7 for Windows Server 2003 Service Pack 1
* Windows Internet Explorer 7 for Windows Server 2003 with SP1 for
Itanium-based Systems
* Windows Internet Explorer 7 for Windows Server 2003 x64 Edition
* Windows Internet Explorer 7 in Windows Vista
DirectAnimation ActiveX Controls Memory Corruption Vulnerabilities -
CVE-2006-4446 and CVE-2006-4777:
Remote code execution vulnerabilities exist in DirectAnimation ActiveX
controls that could be exploited if the ActiveX controls are passed
unexpected data. An attacker could exploit these vulnerabilities by
constructing a specially crafted Web page that could potentially allow
remote code execution if a user visited the specially crafted Web page. An
attacker who successfully exploited these vulnerabilities could take
complete control of an affected system.
Mitigating Factors for DirectAnimation ActiveX Controls Memory Corruption
Vulnerabilities - CVE-2006-4446 and CVE-2006-4777:
* In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit these vulnerabilities. In
addition, compromised Web sites and Web sites that accept or host
user-provided content or advertisements could contain specially crafted
content that could exploit these vulnerabilities. In all cases, however,
an attacker would have no way to force users to visit these Web sites.
Instead, an attacker would have to persuade users to visit the Web site,
typically by getting them to click a link in an e-mail message or instant
messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited these vulnerabilities could gain
the same user rights as the local user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.
* The Restricted sites zone helps reduce attacks that could try to
exploit these vulnerabilities by preventing Active Scripting and ActiveX
controls from being used when reading HTML e-mail. However, if a user
clicks on a link within an e-mail they could still be vulnerable to this
issue through the Web-based attack scenario.
* By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally Outlook 2000
opens HTML e-mail messages in the Restricted sites zone if the Outlook
E-mail Security Update has been installed. Outlook Express 5.5 Service
Pack 2 opens HTML e-mail messages in the Restricted sites zone if
Microsoft Security Bulletin MS04-018 has been installed.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode sets the security level for the Internet zone to High. This is a
mitigating factor for Web sites that have not been added to Internet
Explorer Trusted sites zone. See the FAQ section of this security update
for more information about Internet Explorer Enhanced Security
Configuration
Workarounds for DirectAnimation ActiveX Controls Memory Corruption
Vulnerability - CVE-2006-4446 and CVE-2006-4777:
Microsoft has tested the following workarounds. Although these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.
* Prevent the Microsoft DirectAnimation Path ActiveX control from running
in Internet Explorer
You can help prevent attempts to instantiate this ActiveX control in
Internet Explorer by setting the kill bit for the control in the registry.
Warning If you use Registry Editor incorrectly, you may cause serious
problems that may require you to reinstall your operating system.
Microsoft cannot guarantee that you can solve problems that result from
using Registry Editor incorrectly. Use Registry Editor at your own risk.
For detailed steps that you can use to prevent a control from running in
Internet Explorer, see Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/240797> 240797. Follow these steps in
this article to create a Compatibility Flags value in the registry to
prevent a COM object from being instantiated in Internet Explorer.
To set the kill bit for a CLSID with a value of
{D7A7D7C3-D47F-11D0-89D3-00A0C90833E6}, paste the following text in a text
editor such as Notepad. Then, save the file by using the .reg file name
extension.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX
Compatibility\{D7A7D7C3-D47F-11D0-89D3-00A0C90833E6}]
"Compatibility Flags"=dword:00000400
You can apply this .reg file to individual systems by double-clicking it.
You can also apply it across domains by using Group Policy. For more
information about Group Policy, visit the following Microsoft Web sites:
<http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/6d7cb788-b31d-4d17-9f1e-b5ddaa6deecd.mspx> Group Policy collection
<http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/47ba1311-6cca-414f-98c9-2d7f99fca8a3.mspx> What is Group Policy Object Editor?
<http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/TechRef/e926577a-5619-4912-b5d9-e73d4bdc9491.mspx> Core Group Policy tools and settings
Note You must restart Internet Explorer for your changes to take effect.
Impact of Workaround: Web sites that use the DirectAnimation Path ActiveX
Controls may no longer display or function correctly.
This workaround can also be used for all other CLSIDs for which kill bits
are being set in this security update.
* Configure Internet Explorer to prompt before running ActiveX Controls
or disable ActiveX Controls in the Internet and Local intranet security
zone
You can help protect against these vulnerabilities by changing your
Internet Explorer settings to prompt before running ActiveX controls. 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 Settings, in the ActiveX controls and plug-ins section, under Run
ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the ActiveX controls and plug-ins section, under Run
ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
7. 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 Yes to run ActiveX controls. If you do not want to be
prompted for all these sites, use the steps outlined in "Add sites that
you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone
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 the Internet Explorer
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. 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 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.
Note Add any sites that you trust not to take malicious action on your
computer. Two in particular that you may want to add are
"*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the
quotation marks). These are the sites that will host the update, and it
requires an ActiveX Control to install the update.
* Set Internet and Local intranet security zone settings to High to
prompt before running ActiveX Controls and Active Scripting in these zones
You can help protect against these vulnerabilities by changing your
settings for the Internet security zone to prompt before running ActiveX
controls. You can do this by setting your browser security to High.
To raise the browsing security level in Microsoft Internet Explorer,
follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then
click the Internet icon.
3. Under Security level for this zone, move the slider to High. This sets
the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the
slider to High.
Note Setting the level to High may cause some Web sites to work
incorrectly. If you have difficulty using a Web site after you change this
setting, and you are sure the site is safe to use, you can add that site
to your list of trusted sites. This will allow the site to work correctly
even with the security setting set to High.
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 Yes to run ActiveX controls. If you do not want to be
prompted for all these sites, use the steps outlined in "Add sites that
you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone
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 the Internet Explorer
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. 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 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.
Note Add any sites that you trust not to take malicious action on your
computer. Two in particular that you may want to add are
"*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the
quotation marks). These are the sites that will host the update, and it
requires an ActiveX Control to install the update.
FAQ for DirectAnimation ActiveX Controls Memory Corruption Vulnerabilities
- CVE-2006-4446 and CVE-2006-4777:
What is the scope of the vulnerability?
These are remote code execution vulnerabilities. An attacker who
successfully exploited these vulnerabilities could remotely take complete
control of an affected system. An attacker could then install programs;
view, change, or delete data; or create new accounts with full user
rights.
What causes the vulnerability?
Remote code execution vulnerabilities exist in DirectAnimation ActiveX
controls that could be exploited if the ActiveX controls are passed
unexpected data. This could cause Internet Explorer to fail in a way that
could allow code execution.
What is DirectAnimation?
DirectAnimation as a whole is a deprecated suite of development
functionality. Microsoft recommends using more recent functions in
Microsoft DirectX when developing Web applications and other software that
needs advanced animation. After this security update is installed, Web
applications and software that use DirectAnimation will not function as
expected. One way of accessing the functionality that was exposed in the
DirectAnimation suite was by using HTML+TIME 1.0.
What is HTML+TIME?
HTML+TIME (Timed Interactive Multimedia Extensions) adds timing and media
synchronization support to HTML pages. HTML+TIME 1.0, which is a wrapper
for DirectAnimation, is deprecated functionality and has been replaced by
HTML+TIME 2.0. Customers who use HTML+TIME 1.0 are encouraged to use the
Microsoft implementation of HTML+TIME 2.0 instead. After this security
update is installed, Web applications and software that use HTML+TIME 1.0
will not function as expected.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited these vulnerabilities could gain
the same user rights as the local user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to
exploit these vulnerabilities through Internet Explorer and then persuade
a user to view the Web site. This can also include Web sites that accept
user-provided content or advertisements, Web sites that host user-provided
content or advertisements, and compromised Web sites. These Web sites
could contain specially crafted content that could exploit these
vulnerabilities. In all cases, however, an attacker would have no way to
force users to visit these Web sites. Instead, an attacker would have to
persuade users to visit the Web site, typically by getting them to click a
link in an e-mail message or in an Instant Messenger request that takes
users to the attacker's Web site. It could also be possible to display
specially crafted Web content by using banner advertisements or by using
other methods to deliver Web content to affected systems.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and visits a Web site
for any malicious action to occur. Therefore, any systems where Internet
Explorer is used frequently, such as workstations or terminal servers, are
at the most risk from these vulnerabilities.
I am running Internet Explorer on Windows Server 2003. Does this mitigate
these vulnerabilities?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode sets the security level for the Internet zone to High. This is a
mitigating factor for Web sites that have not been added to Internet
Explorer Trusted sites zone.
What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of
preconfigured Internet Explorer settings that reduce the likelihood of a
user or of an administrator downloading and running specially crafted Web
content on a server. Internet Explorer Enhanced Security Configuration
reduces this risk by modifying many security-related settings. This
includes the settings on the Security tab and the Advanced tab in the
Internet Options dialog box. Some of the important modifications include
the following:
* Security level for the Internet zone is set to High. This setting
disables scripts, ActiveX controls, Microsoft Java Virtual Machine
(MSJVM), and file downloads.
* Automatic detection of intranet sites is disabled. This setting assigns
all intranet Web sites and all Universal Naming Convention (UNC) paths
that are not explicitly listed in the Local intranet zone to the Internet
zone.
* Install On Demand and non-Microsoft browser extensions are disabled.
This setting prevents Web pages from automatically installing components
and prevents non-Microsoft extensions from running.
* Multimedia content is disabled. This setting prevents music,
animations, and video clips from running.
For more information regarding Internet Explorer Enhanced Security
Configuration, see the guide, Managing Internet Explorer Enhanced Security
Configuration, at the following Web site.
What does the update do?
The update removes support for the DirectAnimation Path ActiveX control in
Internet Explorer by setting the kill bit for control. In addition, as a
defense in depth measure, this update sets kill bits for DirectAnimation
as a whole as it is a deprecated suite of development functionality.
Microsoft recommends using Microsoft DirectX and HTML+TIME 2.0 when
developing Web applications and other software.
The Class Identifiers and corresponding files where the DirectAnimation
functionality is contained are as follows.
Class Identifier - File
{D17506C3-6B26-11D0-8914-00C04FC2A0CA} - Danim.dll
{C46C1BCE-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BDE-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BC1-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BE2-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BC6-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BF0-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BEC-3C52-11D0-9200-848C1D000000} - Danim.dll
{50B4791F-4731-11D0-8912-00C04FC2A0CA} - Danim.dll
{25B0F91C-D23D-11D0-9B85-00C04FC2F51D} - Danim.dll
{C46C1BE0-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BD4-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BEE-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BF2-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BD2-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BE6-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BD6-3C52-11D0-9200-848C1D000000} - Danim.dll
{9CDE7341-3C20-11D0-A330-00AA00B92C03} - Danim.dll
{C46C1BF4-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BD0-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BC8-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BD8-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BE4-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BC4-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BCC-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BDC-3C52-11D0-9200-848C1D000000} - Danim.dll
{AF868304-AB0B-11D0-876A-00C04FC29D46} - Danim.dll
{C46C1BCA-3C52-11D0-9200-848C1D000000} - Danim.dll
{C46C1BDA-3C52-11D0-9200-848C1D000000} - Danim.dll
{283807B5-2C60-11D0-A31D-00AA00B92C03} - Danim.dll
{B6FFC24C-7E13-11D0-9B47-00C04FC2F51D} - Danim.dll
{69AD90EF-1C20-11d1-8801-00C04FC29D46} - Danim.dll
{D7A7D7C3-D47F-11D0-89D3-00A0C90833E6} - DaxCtrle.ocx
{4F241DB1-EE9F-11D0-9824-006097C99E51} - DaxCtrle.ocx
{B0A6BAE2-AAF0-11D0-A152-00A0C908DB96} - DaxCtrle.ocx
{FD179533-D86E-11D0-89D6-00A0C90833E6} - DaxCtrle.ocx
{369303C2-D7AC-11D0-89D5-00A0C90833E6} - DaxCtrle.ocx
{BB339A46-7C49-11d2-9BF3-00C04FA34789} - Lmrt.dll
{B1549E58-3894-11D2-BB7F-00A0C999C4C1} - Lmrt.dll
When this security bulletin was issued, had these vulnerabilities been
publicly disclosed?
Yes. These vulnerabilities have been publicly disclosed. They have been
assigned Common Vulnerability and Exposure numbers CVE-2006-4446 and
CVE-2006-4777. This security bulletin addresses the publicly disclosed
vulnerabilities as well as additional issues discovered through internal
investigations.
When this security bulletin was issued, had Microsoft received any reports
that these vulnerabilities were being exploited?
Yes. When the security bulletin was released, Microsoft had received
information that these vulnerabilities were being exploited.
Does applying this security update help protect customers from the code
that has been published publicly that attempts to exploit these
vulnerabilities?
Yes. This security update addresses the vulnerabilities that are currently
being exploited. The vulnerabilities that have been addressed have been
assigned the Common Vulnerability and Exposure number CVE-2006-4446 and
CVE-2006-4777.
HTML Rendering Memory Corruption Vulnerability - CVE-2006-4687:
A remote code execution vulnerability exists in the way Internet Explorer
interprets HTML with certain layout combinations. An attacker could
exploit the vulnerability by constructing a specially crafted Web page
that could potentially allow remote code execution if a user viewed the
Web page. An attacker who successfully exploited this vulnerability could
take complete control of an affected system.
Mitigating Factors for HTML Rendering Memory Corruption Vulnerability -
CVE-2006-4687:
* In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit this vulnerability. In
addition, compromised Web sites and Web sites that accept or host
user-provided content or advertisements could contain specially crafted
content that could exploit this vulnerability. In all cases, however, an
attacker would have no way to force users to visit these Web sites.
Instead, an attacker would have to persuade users to visit the Web site,
typically by getting them to click a link in an e-mail message or instant
messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain
the same user rights as the local user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.
* The Restricted sites zone helps reduce attacks that could try to
exploit this vulnerability by preventing Active Scripting from being used
when reading HTML e-mail messages. However, if a user clicks a link in an
e-mail message, the user could still be vulnerable to this issue through
the Web-based attack scenario.
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML
e-mail messages in the Restricted sites zone. Additionally Outlook 2000
opens HTML e-mail messages in the Restricted sites zone if the Outlook
E-mail Security Update has been installed. Outlook Express 5.5 Service
Pack 2 opens HTML e-mail messages in the Restricted sites zone if
Microsoft Security Bulletin MS04-018 has been installed.
Note It cannot be ruled out that this vulnerability could be used in an
exploit without Active Scripting. However, using Active Scripting
significantly increases the chances of a successful exploit. As a result,
this vulnerability has been given a severity rating of Critical on Windows
Server 2003.
* 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 in the e-mail vector because reading
e-mail messages in plain text is the default configuration for Outlook
Express. See the FAQ section of this security update for more information
about Internet Explorer Enhanced Security Configuration.
Workarounds for HTML Rendering Memory Corruption Vulnerability -
CVE-2006-4687:
Microsoft has tested the following workarounds. Although these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.
Note It cannot be ruled out that this vulnerability could be used in an
exploit without Active Scripting. However, using Active Scripting
significantly increases the chances of a successful exploit. As a result,
this vulnerability has been given a severity rating of Critical on Windows
Server 2003.
* Configure Internet Explorer to prompt before running Active Scripting
or to disable Active Scripting in the Internet and Local intranet security
zone
You can help protect against this vulnerability by changing your settings
to prompt before running Active Scripting or to disable Active Scripting
in the Internet and Local intranet security zone. 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 Settings, in the Scripting section, under Active Scripting, click
Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the Scripting section, under Active Scripting, click
Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.
Note Disabling Active Scripting in the Internet and Local intranet
security zones may cause some Web sites to work incorrectly. If you have
difficulty using a Web site after you change this setting, and you are
sure the site is safe to use, you can add that site to your list of
trusted sites. This will allow the site to work correctly.
Impact of Workaround: There are side effects to prompting before running
Active Scripting. Many Web sites that are on the Internet or on an
intranet use Active Scripting to provide additional functionality. For
example, an online e-commerce site or banking site may use Active
Scripting to provide menus, ordering forms, or even account statements.
Prompting before running Active Scripting 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 Yes to run Active Scripting. If you do not
want to be prompted for all these sites, use the steps outlined in "Add
sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
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 the Internet Explorer
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. 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 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.
Note Add any sites that you trust not to take malicious action on your
computer. Two in particular that you may want to add are
"*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the
quotation marks). These are the sites that will host the update, and it
requires an ActiveX Control to install the update.
* Set Internet and Local intranet security zone settings to High to
prompt before running ActiveX Controls and Active Scripting in these zones
You can help protect against this vulnerability by changing your settings
for the Internet security zone to prompt before running ActiveX controls
and Active Scripting. You can do this by setting your browser security to
High.
To raise the browsing security level in Microsoft Internet Explorer,
follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then
click the Internet icon.
3. Under Security level for this zone, move the slider to High. This sets
the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the
slider to High.
Note Setting the level to High may cause some Web sites to work
incorrectly. If you have difficulty using a Web site after you change this
setting, and you are sure the site is safe to use, you can add that site
to your list of trusted sites. This will allow the site to work correctly
even with the security setting set to High.
Impact of Workaround: There are side effects to prompting before running
ActiveX Controls and Active Scripting. Many Web sites that are on the
Internet or on an intranet use ActiveX or Active Scripting 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 or
Active Scripting 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 Yes to run ActiveX Controls or Active Scripting. If you do
not want to be prompted for all these sites, use the steps outlined in
"Add sites that you trust to the Internet Explorer Trusted sites zone
Add sites that you trust to the Internet Explorer Trusted sites zone.
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 the Internet Explorer
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. 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 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.
Note Add any sites that you trust not to take malicious action on your
computer. Two in particular that you may want to add are
"*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the
quotation marks). These are the sites that will host the update, and it
requires an ActiveX Control to install the update.
* Read e-mail messages in plain text format if you are using Outlook 2002
or a later version, or Outlook Express 6 SP1 or a later version, to help
protect yourself from the HTML e-mail attack vector.
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or
a later version and Microsoft Outlook Express 6 users who have applied
Internet Explorer 6 Service Pack 1 or a later version 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 how to enable this setting in Outlook 2002, see
Microsoft Knowledge Base Article 307594.
For information about this setting in Outlook Express 6, see Microsoft
Knowledge Base Article 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. Additionally:
* 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 HTML Rendering Memory Corruption Vulnerability - CVE-2006-4687:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could remotely take complete
control of an affected system. An attacker could then install programs;
view, change, or delete data; or create new accounts with full user
rights.
What causes the vulnerability?
When Internet Explorer handles specially crafted HTML with certain HTML
layout combinations it may corrupt system memory in such a way that an
attacker could execute arbitrary code.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the
same user rights as the local user. Users whose accounts are configured to
have fewer user rights on the system could be less impacted than users who
operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site or HTML e-mail message
that is designed to exploit this vulnerability through Internet Explorer
and then persuade a user to view the Web site or HTML e-mail message. This
can also include Web sites that accept user-provided content or
advertisements, Web sites that host user-provided content or
advertisements, and compromised Web sites. These Web sites could contain
specially crafted content that could exploit this vulnerability. In all
cases, however, an attacker would have no way to force users to visit
these Web sites. Instead, an attacker would have to persuade users to
visit the Web site, typically by getting them to click a link in an e-mail
message or in an Instant Messenger request that takes users to the
attacker's Web site. It could also be possible to display specially
crafted Web content by using banner advertisements or by using other
methods to deliver Web content to affected systems.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and reading HTML
e-mail messages or that a user is logged on and visits a Web site for any
malicious action to occur. Therefore, any systems where HTML e-mail
messages are read or where Internet Explorer is used frequently, such as
workstations or terminal servers, are at the most risk from this
vulnerability.
Note It cannot be ruled out that this vulnerability could be used in an
exploit without Active Scripting. However, using Active Scripting
significantly increases the chances of a successful exploit. As a result,
this vulnerability has been given a severity rating of Critical on Windows
Server 2003.
What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer decodes certain layout combinations in HTML.
When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.
When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate 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.
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/ms06-067.mspx>
http://www.microsoft.com/technet/security/bulletin/ms06-067.mspx
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