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Microsoft issues Security Advisory for Internet Explorer

Microsoft Security Advisory (2887505)

Vulnerability in Internet Explorer Could Allow Remote Code Execution

General Information

Executive Summary

Microsoft is investigating public reports of a vulnerability in all supported versions of Internet Explorer. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability in Internet Explorer 8 and Internet Explorer 9. Applying the Microsoft Fix it solution, “CVE-2013-3893 MSHTML Shim Workaround,” prevents the exploitation of this issue. See the Suggested Actions section of this advisory for more information.

The vulnerability is a remote code execution vulnerability. The vulnerability exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated. The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer. An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website.

On completion of this investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs.

We are actively working with partners in our Microsoft Active Protections Program (MAPP) to provide information that they can use to provide broader protections to customers. In addition, we are actively working with partners to monitor the threat landscape and take action against malicious sites that attempt to exploit this vulnerability.

Microsoft continues to encourage customers to follow the guidance in the Microsoft Safety & Security Center of enabling a firewall, applying all software updates, and installing antimalware software.

Mitigating Factors:

  • By default, Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability.
  • By default, all supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML email messages in the Restricted sites zone. The Restricted sites zone, which disables script and ActiveX controls, helps reduce the risk of an attacker being able to use this vulnerability to execute malicious code. If a user clicks a link in an email message, the user could still be vulnerable to exploitation of this vulnerability through the web-based attack scenario.
  • An attacker who successfully exploited this vulnerability could gain the same user rights as the current 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.
  • In a web-based attack scenario, an attacker could host a website that contains a webpage that is used to exploit this vulnerability. In addition, compromised websites and websites 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 websites. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email message or Instant Messenger message that takes users to the attacker’s website.

Advisory Details

Issue References

For more information about this issue, see the following references:

References Identification
CVE Reference CVE-2013-3893
Microsoft Knowledge Base Article Microsoft Knowledge Base Article 2887505

Affected Software

This advisory discusses the following software.

Affected Software

Operating System Component
Internet Explorer 6
Windows XP Service Pack 3 Internet Explorer 6
Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 6
Windows Server 2003 Service Pack 2 Internet Explorer 6
Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 6
Windows Server 2003 with SP2 for Itanium-based Systems Internet Explorer 6
Internet Explorer 7
Windows XP Service Pack 3 Internet Explorer 7
Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 7
Windows Server 2003 Service Pack 2 Internet Explorer 7
Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 7
Windows Server 2003 with SP2 for Itanium-based Systems Internet Explorer 7
Windows Vista Service Pack 2 Internet Explorer 7
Windows Vista x64 Edition Service Pack 2 Internet Explorer 7
Windows Server 2008 for 32-bit Systems Service Pack 2 Internet Explorer 7
Windows Server 2008 for x64-based Systems Service Pack 2 Internet Explorer 7
Windows Server 2008 for Itanium-based Systems Service Pack 2 Internet Explorer 7
Internet Explorer 8
Windows XP Service Pack 3 Internet Explorer 8
Windows XP Professional x64 Edition Service Pack 2 Internet Explorer 8
Windows Server 2003 Service Pack 2 Internet Explorer 8
Windows Server 2003 x64 Edition Service Pack 2 Internet Explorer 8
Windows Vista Service Pack 2 Internet Explorer 8
Windows Vista x64 Edition Service Pack 2 Internet Explorer 8
Windows Server 2008 for 32-bit Systems Service Pack 2 Internet Explorer 8
Windows Server 2008 for x64-based Systems Service Pack 2 Internet Explorer 8
Windows 7 for 32-bit Systems Service Pack 1 Internet Explorer 8
Windows 7 for x64-based Systems Service Pack 1 Internet Explorer 8
Windows Server 2008 R2 for x64-based Systems Service Pack 1 Internet Explorer 8
Windows Server 2008 R2 for Itanium-based Systems Service Pack 1 Internet Explorer 8
Internet Explorer 9
Windows Vista Service Pack 2 Internet Explorer 9
Windows Vista x64 Edition Service Pack 2 Internet Explorer 9
Windows Server 2008 for 32-bit Systems Service Pack 2 Internet Explorer 9
Windows Server 2008 for x64-based Systems Service Pack 2 Internet Explorer 9
Windows 7 for 32-bit Systems Service Pack 1 Internet Explorer 9
Windows 7 for x64-based Systems Service Pack 1 Internet Explorer 9
Windows Server 2008 R2 for x64-based Systems Service Pack 1 Internet Explorer 9
Internet Explorer 10
Windows 7 for 32-bit Systems Service Pack 1 Internet Explorer 10
Windows 7 for x64-based Systems Service Pack 1 Internet Explorer 10
Windows Server 2008 R2 for x64-based Systems Service Pack 1 Internet Explorer 10
Windows 8 for 32-bit Systems Internet Explorer 10
Windows 8 for 64-bit Systems Internet Explorer 10
Windows Server 2012 Internet Explorer 10
Windows RT Internet Explorer 10
Internet Explorer 11
Windows 8.1 for 32-bit Systems Internet Explorer 11
Windows 8.1 for 64-bit Systems Internet Explorer 11
Windows Server 2012 R2 Internet Explorer 11
Windows RT 8.1 Internet Explorer 11

Non-Applicable Software

Operating System Component
Server Core installation
Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) Not applicable
Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) Not applicable
Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) Not applicable
Windows Server 2012 (Server Core installation) Not applicable
Windows Server 2012 R2 (Server Core installation) Not applicable

Advisory FAQ

What is the scope of the advisory?
Microsoft is investigating public reports of a vulnerability in all supported versions of Internet Explorer.

Is this a security vulnerability that requires Microsoft to issue a security update?
On completion of our investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the current user. If the current 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.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website. The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements. These websites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically by getting them to click a link in an email message or in an Instant Messenger message that takes users to the attacker’s website, or by opening an attachment sent through email.

I am running Internet Explorer for Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012 or Windows Server 2012 R2. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003, Windows Server 2008, and Windows Server 2008 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

Does EMET help mitigate attacks that try to exploit this vulnerability?
Yes. The Enhanced Mitigation Experience Toolkit (EMET) enables users to manage security mitigation technologies that help make it more difficult for attackers to exploit vulnerabilities in a given piece of software. EMET helps to mitigate this vulnerability in Internet Explorer on systems where EMET is installed and configured to work with Internet Explorer.

For more information about EMET, see The Enhanced Mitigation Experience Toolkit.

Apply Workarounds
Workarounds refer to a setting or configuration change that does not correct the underlying issue but would help block known attack vectors before a security update is available. See the next section, Workarounds, for more information.

Workarounds refer to a setting or configuration change that does not correct the underlying issue but would help block known attack vectors before a security update is available. See the next section, Workarounds, for more information.

Workarounds
  • Apply the Microsoft Fix it solution, “CVE-2013-3893 MSHTML Shim Workaround”, that prevents exploitation of this issueSee Microsoft Knowledge Base Article 2887505 to use the automated Microsoft Fix it solution to enable or disable this workaround.

     

  • Deploy the Enhanced Mitigation Experience Toolkit The Enhanced Mitigation Experience Toolkit (EMET) helps mitigate the exploitation of this vulnerability by adding additional protection layers that make the vulnerability harder to exploit. EMET 3.0 and EMET 4.0 are officially supported by Microsoft. At this time, EMET is only available in the English language. For more information, see Microsoft Knowledge Base Article 2458544.

    For more information about configuring EMET, see the EMET User’s Guide:

    • On 32-bit systems the EMET User’s Guide is located in C:\Program Files\EMET\EMET User’s Guide.pdf
    • On 64-bit systems the EMET User’s Guide is located in C:\Program Files (x86)\EMET\EMET User’s Guide.pdf

    Configure EMET 4.0 for Internet Explorer

    EMET 4.0, in the recommended configuration, is automatically configured to help protect Internet Explorer. No additional steps are required.

    Configure EMET 3.0 for Internet Explorer from the EMET user interface

    To add iexplore.exe to the list of applications using EMET, perform the following steps:

    1. Click Start, All Programs, Enhanced Mitigation Experience Toolkit, and EMET 3.0.
    2. Click Yes on the UAC prompt, click Configure Apps, then select Add. Browse to the application to be configured in EMET.
    3. On 64-bit versions of Microsoft Windows, the paths to 32-bit and x64 installations of Internet Explorer are:C:\Program Files (x86)\Internet Explorer\iexplore.exe

      C:\Program Files\Internet Explorer\iexplore.exe

      On 32-bit versions of Microsoft Windows, the path to Internet Explorer is

      C:\Program Files\Internet Explorer\iexplore.exe

    4. Click OK and exit EMET.

    Configure EMET 3.0 for Internet Explorer from a command line

    • Opt in Internet Explorer to all EMET 3.0 mitigations
    • On 64-bit systems, for 32-bit installations of IE run the following from an elevated command prompt:"c:\Program Files (x86)\EMET\EMET_Conf.exe" --set "c:\Program Files (x86)\Internet Explorer\iexplore.exe"

      And on 64-bit systems, for x64 installations of IE run the following from an elevated command prompt:

      "c:\Program Files (x86)\EMET\EMET_Conf.exe" --set "c:\Program Files\Internet Explorer\iexplore.exe"

    • On 32-bit systems, for 32-bit installations of IE run the following from an elevated command prompt:"c:\Program Files\EMET\EMET_Conf.exe" --set "c:\Program Files\Internet Explorer\iexplore.exe"
    • If you have completed this successfully, the following message appears:"The changes you have made may require restarting one or more applications"
    • If the application has already been added in EMET, the following message appears:Error: "c:\Program Files (x86)\Internet Explorer\iexplore.exe" conflicts with existing entry for "C:\Program Files (x86)\Internet Explorer\iexplore.exe"
    • For more information regarding running EMET_Conf.exe, see the command line help by running the following from a command prompt.On 32-bit systems:

      "C:\Program Files\EMET\EMET_Conf.exe" /?

      On 64-bit systems:

      "C:\Program Files (x86)\EMET\EMET_Conf.exe" /?

    Configure EMET for Internet Explorer using Group Policy

    EMET can be configured using Group Policy. For information about configuring EMET using Group Policy, see the EMET User’s Guide:

    • On 32-bit systems the EMET User’s Guide is located in C:\Program Files\EMET\EMET User’s Guide.pdf
    • On 64-bit systems the EMET User’s Guide is located in C:\Program Files (x86)\EMET\EMET User’s Guide.pdf

    Note For more information about Group Policy, see Group Policy collection.

     

  • Set Internet and Local intranet security zone settings to “High” to block ActiveX Controls and Active Scripting in these zonesYou can help protect against exploitation of this vulnerability by changing your settings for the Internet security zone to block ActiveX controls and Active Scripting. You can do this by setting your browser security to High.

    To raise the browsing security level in Internet Explorer, perform the following 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 Internet.
    3. Under Security level for this zone, move the slider to High. This sets the security level for all websites you visit to High.
    4. Click Local intranet.
    5. Under Security level for this zone, move the slider to High. This sets the security level for all websites you visit to High.
    6. Click OK to accept the changes and return to Internet Explorer.

    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 websites to work incorrectly. If you have difficulty using a website 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 blocking ActiveX Controls and Active Scripting. Many websites 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. Blocking ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. If you do not want to block ActiveX Controls or Active Scripting for such 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 block 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 websites exactly as you do today, while helping to protect yourself from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

    To do this, perform the following 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 website 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 system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.

     

  • Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zoneYou can help protect against exploitation of 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, perform the following 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 websites to work incorrectly. If you have difficulty using a website 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 websites 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 websites 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, perform the following 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 website 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 system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.

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