Microsoft is investigating public reports of a vulnerability in Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8. Internet Explorer 9 and Internet Explorer 10 are not affected by the vulnerability. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability through Internet Explorer 8. Applying the Microsoft Fix it solution, “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 that 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.
The Fix it solution that is described in this section is not intended to be a replacement for any security update. We recommend that you always install the latest security updates. However, we offer this Fix it solution as a workaround option for some scenarios.
For more information about this workaround, go to the following Microsoft Security Advisory webpage:
The advisory provides more information about the issue, including the following:
- The scenarios in which you might apply or disable the workaround.
- How to manually apply the workaround.
Specifically, to see this information, look for the General Information heading, expand the Suggested actions section, and then expand the Workaround section.
To enable or disable this Fix it solution, click the Fix it button or link under the Enable heading or under the Disable heading. Click Run in the File Download dialog box, and then follow the steps in the Fix it wizard.
| Enable MSHTML shim workaround | Disable MSHTML shim workaround |
|---|---|
|
Fix this problem
Microsoft Fix it 50971 |
Fix this problem
Microsoft Fix it 50972 |
Notes
- These wizards may be in English only. However, the automatic fixes also work for other language versions of Windows.
- If you are not on the computer that has the problem, you can save the automatic fix to a flash drive or to a CD, and then you can run it on the computer that has the problem.
- If you want to run a quiet installation of this Fix it solution, follow these steps:
- Open an elevated Command Prompt window with administrator credentials.
- Type the following command, and then press Enter:
msiexec /i MicrosoftFixit50971.msi /quiet
Deploying an application compatibility database across multiple computers
To deploy an application compatibility database across multiple computers, you can use a system management solution, such as Microsoft System Center Configuration Manager 2007, and then use the SDBInst.exe command-line tool to install the database. For detailed information about how to use the SDBInst application, go to the following TechNet webpage:
To deploy Microsoft Fix it 50971 to multiple computers by using SDBInst, follow these steps:
Note For more information about command-line options for installing this fix, see the following MSDN webpage:
- Extract the CAB file from the Fix it package. To do this, type the following command at a command prompt:
msidb.exe -x CabFile -d MicrosoftFixit50971.msi
Note Msidb.exe is part of Windows Installer Development Tools. For more information, go to the following Microsoft webpage:
- Extract the SDB files from CabFile by using any CAB extraction utility:
extract.exe /E CabFile
- Use SDBInst to apply the previously extracted .sdb files. To do this, type the following command at a command prompt:
SDBInst -p Path_of_sdb_file\FileName.sdb
File hash table
The following table lists the thumbprints of the certificates that are used to sign the .sdb files. Verify the certificate thumbprint in this table against the certificate thumbprint that is indicated on the .sdb that you extracted.
File Name Hash information mshtml_shim32.sdb (SHA1 695750970F6595D247FA30775579BD22E034252B) mshtml_shim64.sdb (SHA1 29444332522F8F06A88953071B3BA13C14FBD70A)
Technical Details:
- 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. 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.
Recommendation. Please see the Suggested Actions section of this advisory for more information.
Advisory Details
Issue References
For more information about this issue, see the following references:
| References | Identification |
|---|---|
| CVE Reference | CVE-2012-4792 |
| Microsoft Knowledge Base Article | Microsoft Knowledge Base Article 2794220 |
Affected and Non-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 | Internet Explorer 8 |
| Windows 7 for 32-bit Systems Service Pack 1 | Internet Explorer 8 |
| Windows 7 for x64-based Systems | Internet Explorer 8 |
| Windows 7 for x64-based Systems Service Pack 1 | Internet Explorer 8 |
| Windows Server 2008 R2 for x64-based Systems | 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 | Internet Explorer 8 |
| Windows Server 2008 R2 for Itanium-based Systems Service Pack 1 | Internet Explorer 8 |
Non-Affected Software
| Operating System | Component |
|---|---|
| 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 | Internet Explorer 9 |
| Windows 7 for 32-bit Systems Service Pack 1 | Internet Explorer 9 |
| Windows 7 for x64-based Systems | Internet Explorer 9 |
| Windows 7 for x64-based Systems Service Pack 1 | Internet Explorer 9 |
| Windows Server 2008 R2 for x64-based Systems | Internet Explorer 9 |
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 | Internet Explorer 9 |
| 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 |
| 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 (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 |
Frequently Asked Questions
Suggested Actions
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
- Apply the Microsoft Fix it solution, “MSHTML Shim Workaround”, that prevents exploitation of this issueSee Microsoft Knowledge Base Article 2794220 to use the automated Microsoft Fix it solution to enable or disable this workaround.
- Deploy the Enhanced Mitigation Experience ToolkitThe Enhanced Mitigation Experience Toolkit (EMET) helps mitigate the exploitation of this vulnerability by adding additional protection layers that make the vulnerability harder to exploit.
At this time, EMET is provided with limited support and 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 for Internet Explorer from the EMET user interface
To add iexplore.exe to the list of applications using EMET, perform the following steps:
- Click Start, All Programs, Enhanced Mitigation Experience Toolkit, and EMET 3.0.
- Click Yes on the UAC prompt, click Configure Apps, then select Add. Browse to the application to be configured in EMET.
- 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.exeC:\Program Files\Internet Explorer\iexplore.exeOn 32-bit versions of Microsoft Windows, the path to Internet Explorer is
C:\Program Files\Internet Explorer\iexplore.exe - Click OK and exit EMET.
Configure EMET 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 displays:
"The changes you have made may require restarting one or more applications" - If the application has already been added in EMET, the following message displays:
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:
- On the Internet Explorer Tools menu, click Internet Options.
- In the Internet Options dialog box, click the Security tab, and then click Internet.
- Under Security level for this zone, move the slider to High. This sets the security level for all websites you visit to High.
- Click Local intranet.
- Under Security level for this zone, move the slider to High. This sets the security level for all websites you visit to High.
- 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:
- In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
- In the Select a web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
- 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.
- In the Add this website to the zone box, type the URL of a site that you trust, and then click Add.
- Repeat these steps for each site that you want to add to the zone.
- 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:
- In Internet Explorer, click Internet Options on the Tools menu.
- Click the Security tab.
- Click Internet, and then click Custom Level.
- Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
- Click Local intranet, and then click Custom Level.
- Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
- 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:
- In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
- In the Select a web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
- 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.
- In the Add this website to the zone box, type the URL of a site that you trust, and then click Add.
- Repeat these steps for each site that you want to add to the zone.
- 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.
Additional Suggested Actions
- Keep Third-party Software UpdatedCurrent exploits of this type of vulnerability in Internet Explorer use third-party software, including Oracle’s Java, to help obtain reliable exploitation.
For more information about keeping Java updated, see the following:
- Protect your PCWe continue to encourage customers to follow our Protect Your Computer guidance of enabling a firewall, getting software updates and installing antivirus software. For more information, see Microsoft Safety & Security Center.
- Keep Microsoft Software UpdatedUsers running Microsoft software should apply the latest Microsoft security updates to help make sure that their computers are as protected as possible. If you are not sure whether your software is up to date, visit Microsoft Update, scan your computer for available updates, and install any high-priority updates that are offered to you. If you have automatic updating enabled and configured to provide updates for Microsoft products, the updates are delivered to you when they are released, but you should verify that they are installed.
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