[NT] Cumulative Security Update for Internet Explorer (MS05-038)

From: SecuriTeam (support_at_securiteam.com)
Date: 08/10/05

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      Cumulative Security Update for Internet Explorer (MS05-038)
    ------------------------------------------------------------------------

    SUMMARY

    A buffer overflow vulnerability within Internet Explorer allows attackers
    to execute arbitrary code. A cross site scripting within Internet Explorer
    that could allow information disclosure or remote code execution on an
    affected system. A remote code execution vulnerability exists in the way
    Internet Explorer instantiates COM Objects that are not intended to be
    used in Internet Explorer.

    DETAILS

    Vulnerable Systems:
     * Microsoft Windows 2000 Service Pack 4
     * Microsoft Windows XP Service Pack 1 and 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 Service Pack 1 for Itanium-based Systems
     * Microsoft Windows Server 2003 x64 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.
     * Internet Explorer 5.01 Service Pack 4 on Microsoft Windows 2000 Service
    Pack 4 <> Download the update
     * Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service
    Pack 4 or on Microsoft Windows XP Service Pack 1
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=68300B15-1CF9-45FB-875E-2EF6D2FBC9ED> Download the update
     * Internet Explorer 6 for Microsoft Windows XP Service Pack 2
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=648B6F0E-1695-44E5-826A-43406DF4858E> Download the update
     * Internet Explorer 6 for Microsoft Windows Server 2003 and Microsoft
    Windows Server 2003 Service Pack 1
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=F0B96EC3-E954-423A-9AB0-5712B9F14637> Download the update
     * Internet Explorer 6 for Microsoft Windows Server 2003 for Itanium-based
    Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based
    Systems
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=C24D3738-213A-41B8-84A3-2842B34D7B10> Download the update
     * Internet Explorer 6 for Microsoft Windows Server 2003 x64 Edition
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=F2D544E7-33F5-4A65-A574-15495B05B883> Download the update
     * Internet Explorer 6 for Microsoft Windows XP Professional x64 Edition
     
    <http://www.microsoft.com/downloads/details.aspx?FamilyId=1181BC67-0A1D-4A06-99AC-5B2BC6DFE0F6> Download the update
     * Internet Explorer 5.5 Service Pack 2 on Microsoft Windows Millennium
    Edition Review the FAQ section of this bulletin for details about this
    version.
     * Internet Explorer 6 Service Pack 1 on Microsoft Windows 98, on
    Microsoft Windows 98 SE, or on Microsoft Windows Millennium Edition
    Review the FAQ section of this bulletin for details about this version.

    JPEG Image Rendering Memory Corruption Vulnerability - CAN-2005-1988:
    A remote code execution vulnerability exists in Internet Explorer because
    of the way that it handles JPEG images. An attacker could exploit the
    vulnerability by constructing a malicious JPEG image that could
    potentially allow remote code execution if a user visited a malicious Web
    site or viewed a malicious e-mail message. An attacker who successfully
    exploited this vulnerability could take complete control of an affected
    system.

    Mitigating Factors for JPEG Image Rendering Memory Corruption
    Vulnerability - CAN-2005-1988:
    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 could also try to compromise a Web site and have it display
    malicious content. An attacker would have no way to force users to visit a
    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 or to a site that has been compromised by the attacker.

     * 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.

     * By default, Internet Explorer on Windows Server 2003 runs in a
    restricted mode that is known as
    <http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp> Enhanced Security Configuration. This mode mitigates this vulnerability where the e-mail vector is concerned although clicking on a link would still put users at risk. In Windows Server 2003, Microsoft Outlook Express uses plain text for reading and sending messages by default. When replying to an e-mail message that is sent in another format, the response is formatted in plain text. See the FAQ section of this vulnerability for more information about Internet Explorer Enhanced Security Configuration.

    Workarounds for JPEG Image Rendering Memory Corruption Vulnerability -
    CAN-2005-1988:
    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
    in the following section.

      Read e-mail messages in plain text format if you are using Microsoft
    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
    <http://support.microsoft.com/kb/307594> Microsoft Knowledge Base Article
    307594.

     * For information about this setting in Outlook Express 6, see
    <http://support.microsoft.com/kb/291387> 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 JPEG Image Rendering Memory Corruption Vulnerability -
    CAN-2005-1988:
    What is the scope of the vulnerability?
    If a user is logged on with administrative user rights, an attacker who
    successfully exploited this vulnerability 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.

    What causes the vulnerability?
    When Internet Explorer displays a specially formed JPEG image, it may
    corrupt system memory in such a way that an attacker could execute
    arbitrary code.

    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. If the user visited the page or
    viewed the e-mail message, the attacker could access information from
    other Web sites, could access local files in predetermined locations on
    the system, or could cause malicious code to run in the security context
    of the locally logged on user. An attacker could also try to compromise a
    Web site and have it display malicious content.

    What systems are primarily at risk from the vulnerability?
    This vulnerability requires that a user is logged on and 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 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.

    I am running Internet Explorer on Windows Server 2003. Does this mitigate
    this vulnerability?
    Yes. 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 where the e-mail vector is concerned
    although clicking on a link would still put users at risk. In Windows
    Server 2003, Microsoft Outlook Express uses plain text for reading and
    sending messages by default. When replying to an e-mail message that is
    sent in another format, the response is formatted in plain text.

    What is 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 malicious 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), HTML
    content, 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.

    What does the update do?
    The update removes the vulnerability by modifying the way that 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?
    Yes. This vulnerability has been publicly disclosed. It has been assigned
    Common Vulnerability and Exposure number CAN-2005-1988.

    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.

    Web Folder Behaviors Cross-Domain Vulnerability - CAN-2005-1989:
    A cross-domain vulnerability exists in Internet Explorer that could allow
    information disclosure or remote code execution on an affected system. An
    attacker could exploit the vulnerability by constructing a malicious Web
    page. The malicious Web page could potentially allow remote code execution
    if it is viewed by a user. An attacker who successfully exploited this
    vulnerability could take complete control of an affected system. However,
    significant user interaction and social engineering is required to exploit
    this vulnerability.

    Mitigating Factors for Web Folder Behaviors Cross-Domain Vulnerability -
    CAN-2005-1989:
    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 could also attempt to compromise a Web site to have it display a
    Web page that contains malicious content. An attacker would have no way to
    force users to visit a 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 or to a site that has been
    compromised by the attacker.

    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 and ActiveX controls
    from being used when reading HTML e-mail messages. However, if a user
    clicks a link in an e-mail message, 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 98 and
    Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
     <http://go.microsoft.com/fwlink/?LinkId=33334> 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 <http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been
    installed.

    By default, Internet Explorer on Windows Server 2003 runs in a restricted
    mode that is known as
    <http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp> Enhanced Security Configuration. This mode mitigates this vulnerability. See the FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.

    Windows XP Service Pack 2 introduced a security enhancement known as the
    <http://msdn.microsoft.com/security/productinfo/XPSP2/securebrowsing/locallockdown.aspx> Local Machine zone lockdown. This security enhancement mitigates this vulnerability when the Local Machine Zone is the target of an attack. See the FAQ section of this security update for more information about the Local Machine zone lockdown.

    Workarounds for Web Folder Behaviors Cross-Domain Vulnerability -
    CAN-2005-1989:
    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
    in the following section.

    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 high security setting.

    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 "Restrict Web sites to only your
    trusted Web sites" workaround.

    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 this vulnerability by changing your settings
    to prompt before running ActiveX controls only. 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.
      5. In the Scripting section, under Active Scripting, click Prompt, and
    then click OK.
      6. Click Local intranet, and then click Custom Level.
      7. Under Settings, in the ActiveX controls and plug-ins section, under
    Run ActiveX controls and plug-ins, click Prompt.
      8. In the Scripting section, under Active Scripting, 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 Yes to 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. 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.

    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 quotation marks). This is the
    site that will host the update, and it requires an ActiveX control to
    install the update.

    FAQ for Web Folder Behaviors Cross-Domain Vulnerability - CAN-2005-1989:
    What is the scope of the vulnerability?
    This is a cross-domain vulnerability that could allow information
    disclosure or remote code execution. If a user is logged on with
    administrative privileges, an attacker who successfully exploited this
    vulnerability 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 privileges. Users whose accounts are
    configured to have fewer privileges on the system could be less impacted
    than users who operate with administrative privileges.

    What causes the vulnerability?
    The process by which certain URLs are interpreted when browsing from a Web
    page to a Web folder view using WebDAV. This process is handled by the Web
    Folder Behaviors in Internet Explorer. URLs are not properly validated by
    the Internet Explorer cross-domain security model.

    What are Web Folder Behaviors?
    Web Folder Behaviors are available in Microsoft Internet Explorer 5 and
    later versions. Web Folder Behaviors allow users to browse to a folder
    view, and include support for
    <http://support.microsoft.com/support/kb/articles/q221/6/00.asp>
    Distributed Authoring and Versioning (DAV) and Web Extender Client (WEC)
    protocols. For more information about Web Folder Behaviors, see the
    <http://msdn.microsoft.com/library/default.asp?url=/workshop/author/behaviors/overview/webfolder.asp> product documentation.

    What are Internet Explorer security zones?
    Internet Explorer
    <http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q174360> security
    zones are part of a system that divides online content into categories or
    zones, based on the trustworthiness of the content. Specific Web domains
    can be assigned to a zone, depending on how much trust is put 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 or another
    security zone or domain 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 and then persuading the user to visit this page When the user visited
    the page and interacted with the Web page, the attacker could access
    information from other Web sites, could access local files on the system,
    or could cause script to run in the security context of the Local Machine
    zone or another security zone or domain.

    What systems are primarily at risk from the vulnerability?
    This vulnerability requires that a user view a Web site for malicious
    action to occur and accept a prompt for adding an Internet Explorer
    favorite to their system. Therefore, any systems where Internet Explorer
    is used frequently, such as workstations or terminal servers, are at the
    most risk from this vulnerability. Systems that are not typically used to
    visit Web sites, such as most server systems, are at a reduced risk.

    I am running Internet Explorer on Windows Server 2003. Does this mitigate
    this vulnerability?
    Yes. By default, Internet Explorer on Windows Server 2003 runs in a
    restricted mode that is known as
    <http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp> Enhanced Security Configuration. This mode mitigates this vulnerability.

    What is 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 malicious 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), HTML
    content, 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.

    I am running Internet Explorer on Windows XP Service Pack 2. Does this
    mitigate this vulnerability?
    Yes. Windows XP Service Pack 2 introduced a security enhancement known as
    the
    <http://msdn.microsoft.com/security/productinfo/XPSP2/securebrowsing/locallockdown.aspx> Local Machine zone lockdown that mitigates this vulnerability when the Local Machine Zone is the target of an attack.

    What is the Local Machine zone lockdown?
    In Windows XP Service Pack 2, all local files and content that are
    processed by Internet Explorer have additional security restrictions
    applied to them in the Local Machine zone. This feature restricts HTML in
    the Local Machine zone. This feature also restricts HTML that is hosted in
    Internet Explorer. These restrictions help mitigate attacks where the
    Local Machine zone is used as an attack vector to load malicious HTML
    code.

    Because of this change, ActiveX script in local HTML pages that is viewed
    inside Internet Explorer will not run. Also, script in local HTML pages
    that is viewed inside Internet Explorer prompts the user for permission 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 the following
    Web site.

    What does the update do?
    The update removes the vulnerability by making sure that the Internet
    Explorer cross-domain security model is enforced when navigating from a
    Web page to a Web folder view in Internet Explorer.

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

    COM Object Instantiation Memory Corruption Vulnerability - CAN-2005-1990:
    A remote code execution vulnerability exists in the way Internet Explorer
    instantiates COM Objects that are not intended to be used in Internet
    Explorer. An attacker could exploit the vulnerability by constructing a
    malicious Web page that could potentially allow remote code execution if a
    user visited the malicious Web site. An attacker who successfully
    exploited this vulnerability could take complete control of an affected
    system.

    Mitigating Factors for COM Object Instantiation Memory Corruption
    Vulnerability - CAN-2005-1990:
    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 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 ActiveX controls from being used when
    reading HTML e-mail messages. However, if a user clicks a link in an
    e-mail message, 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 98 and
    Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the
     <http://go.microsoft.com/fwlink/?LinkId=33334> 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 <http://go.microsoft.com/fwlink/?LinkId=19527> MS04-018 has been
    installed.

    By default, Internet Explorer on Windows Server 2003 runs in a restricted
    mode that is known as
    <http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp> Enhanced Security Configuration. This mode mitigates this vulnerability. See the FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.

    Workarounds for COM Object Instantiation Memory Corruption Vulnerability -
    CAN-2005-1990:
    Microsoft has tested the following workarounds. While these workarounds
    will not correct the underlying vulnerability, they help block known
    attack vectors. The workarounds are mutually exclusive. Users need only
    apply one workaround. When a workaround reduces functionality, it is
    identified in the following section.

    Set Internet and Local intranet security zone settings to High to prompt
    before running ActiveX controls 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.
    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.

    Repeat steps 1 through 3 for the Local intranet security zone by clicking
    the Local intranet icon.

    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: User will be prompted prior to running ActiveX
    controls unless the Web site is in the user s list of trusted sites.

    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 this vulnerability by changing your settings
    to prompt before running ActiveX controls or disable ActiveX controls in
    the Internet and Local intranet security zone. To do this, 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. 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.

    FAQ for COM Object Instantiation Memory Corruption Vulnerability -
    CAN-2005-1990:
    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 tries to instantiate certain COM objects as ActiveX
    controls, the COM Objects 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 take
    complete control of the affected system. In a Web-based attack scenario,
    an attacker would host a Web site that exploits 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. It could also be possible to display malicious Web
    content by using banner advertisements or by using other methods to
    deliver Web content to affected systems.

    How could an attacker exploit the vulnerability?
    An attacker could host a malicious Web site that is designed to exploit
    this vulnerability through Internet Explorer and then persuade a user to
    view the Web site.

    What systems are primarily at risk from the vulnerability?
    This vulnerability requires that a user is logged on and reading e-mail
    messages or by visiting Web sites for any malicious action to occur.
    Therefore, any systems where 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.

    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. The security updates are
    available from the <http://go.microsoft.com/fwlink/?LinkId=21130> Windows
    Update Web site. For more information about severity ratings, visit the
    following <http://go.microsoft.com/fwlink/?LinkId=21140> Web site.

    What does the update do?
    Because not all COM objects have been are not designed to be accessed
    through Internet Explorer, this update sets the
    <http://support.microsoft.com/kb/240797> kill bit for a list of Class
    identifiers (CLSIDs) in COM objects that have been found to exhibit
    similar behavior to the JVIEW Profiler vulnerability that is addressed in
    <http://go.microsoft.com/fwlink/?linkid=50122> Microsoft Security Bulletin
    MS05-037. To help protect customers, this update prevents these CLSIDs
    from being instantiated in Internet Explorer. For more information about
    kill bits, see <http://support.microsoft.com/kb/240797> Microsoft
    Knowledge Base Article 240797.

    When this security bulletin was issued, had this vulnerability been
    publicly disclosed?
    The vulnerability addressed in
    <http://go.microsoft.com/fwlink/?linkid=50122> Microsoft Security Bulletin
    MS05-037 had been publicly disclosed. However, none of the CLSIDs that are
    addressed in this bulletin had been publicly disclosed.

    When this security bulletin was issued, had Microsoft received any reports
    that this vulnerability was being exploited?
    When the security bulletin was released, Microsoft had received
    information that the vulnerability that is addressed in
    <http://go.microsoft.com/fwlink/?linkid=50122> Microsoft Security Bulletin
    MS05-037 had been exploited. Microsoft had not received information that
    any of the CLSIDs that are addressed in this bulletin had been exploited.

    Does applying this security update help protect customers from the code
    that has been published publicly that attempts to exploit this
    vulnerability?
    This security update addresses the vulnerability that is currently being
    exploited and that was addressed in
    <http://go.microsoft.com/fwlink/?linkid=50122> Microsoft Security Bulletin
    MS05-037.

    CVE Information:
     <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1988>
    CAN-2005-1988
     <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1989>
    CAN-2005-1989
     <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1990>
    CAN-2005-1990

    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/MS05-038.mspx>
    http://www.microsoft.com/technet/security/Bulletin/MS05-038.mspx

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