Microsoft Security Bulletin MS11-024 - Important

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:

• On all supported editions of Windows XP and Windows Server 2003, the Windows Fax Cover Page Editor is not installed by default. For the Windows Fax Cover Page Editor to be available, the Fax Services component of these operating systems would need to be enabled.
• On all supported editions of Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2, by default, the affected file type (.cov) is not registered to any program. For an attack to be successful, a user would first need to open the Windows Fax Cover Page Editor and then open a specially crafted .cov file.
• The vulnerability cannot be exploited automatically through e-mail. For an attack to be successful, a user must open an attachment that is sent in an e-mail message.
• An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on 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 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 convince 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.

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

• Remove the Fax Cover Page .COV file association on Windows XP and Windows Server 2003

  If the .cov file type has been associated with the Windows Fax Cover Page Editor, removing the file association prevents the file from being automatically opened.

  Note 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

  To remove the fax cover page (.cov) file association, perform the following steps:

  Using the interactive method

  1. Click Start, click Run, type regedit, and then click OK.
  2. Expand HKEY_CLASSES_ROOT, click on .COV, and then click the File menu and select Export.
  3. In the Export Registry File dialog box, type Cover_Page_Backup.reg and click Save.
     
     Note This will create a backup of this registry key in the My Documents folder by default.
  4. Press the Delete key on the keyboard to delete the registry key. When prompted to delete the registry value, click Yes.

  Using a managed deployment script

  1. Make a backup copy of the registry key using the following command:
     
     Regedit.exe /e cover_page_backup.reg HKEY_CLASSES_ROOT\.COV
  2. Save the following to a file with a .REG extension (e.g. Delete_Cover_Page_Assoc.reg):
     
     Windows Registry Editor Version 5.00

[-HKEY_CLASSES_ROOT\.COV]
  3. Run the registry script created in the previous step with the following command:
     
     Regedit.exe /s delete_cover_page.reg

  Impact of workaround. This workaround removes the .COV file association. Double-clicking a COV file will no longer launch Windows Fax Cover Page Editor.

  How to undo the workaround.

  Using the interactive method

  1. Click Start, click Run, type Regedit in the Open box, and then click OK.
  2. Click the File menu and select Import.
  3. In the Import Registry File dialog box, select Cover_Page_Backup.reg and click Open.

  Using a managed deployment script

  Restore the original state by running the following command:
  
  Regedit.exe /s cover_page_backup.reg

What is the scope of the vulnerability? 
This is a remote code execution vulnerability. 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.

What causes the vulnerability? 
The vulnerability is caused when the Windows Fax Cover Page Editor does not properly parse a specially crafted fax cover page.

What is the Windows Fax Cover Page Editor? 
The Fax Cover Page Editor (fxscover.exe) application can be used to create and edit fax cover pages.

In all supported editions of Windows XP and Windows Server 2003, the Windows Fax Cover Page Editor is only available if the optional Fax Services component is enabled. The Fax Services component is not installed by default on these operating systems. For information about enabling the Fax Services component of Microsoft Windows XP, see Microsoft Knowledge Base Article 306550.

In supported versions of Windows Vista Enterprise Edition, the Windows Fax Cover Page Editor is available as an optional component. In supported versions of Windows Vista Business Edition and Windows Vista Ultimate Edition, and in all supported editions of Windows 7, the Windows Fax Cover Page Editor is available by default. In supported versions of Windows Server 2008 (32-bit and x64-based only) and Windows Server 2008 R2 (x64-based only), the Fax Cover Page Editor is available if the Fax Server role is enabled. Typically, on these operating systems, the Windows Cover Page Editor is launched from within the Windows Fax and Scan application or from the Fax Service Manager when a user creates or edits a fax cover page. For more information on creating and editing fax cover pages, see Create or edit a fax cover page and the TechNet article, Managing Cover Pages.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could run arbitrary code as the logged-on user. If a user is logged on with administrative user rights, an attacker could take complete control of the 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.

How could an attacker exploit the vulnerability? 
For an attacker to exploit this vulnerability, a user would need to open a specially crafted fax cover page file (.cov) using the Windows Fax Cover Page Editor.

In an e-mail attack scenario, an attacker could exploit the vulnerability by sending a specially crafted fax cover page file (.cov) to the user and by convincing the user to open the file within the Windows Fax Cover Page Editor application.

In a Web-based attack scenario, an attacker would have to host a Web site that contains a specially crafted fax cover page file (.cov) that is used to attempt to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site, and then convince them to open the specially crafted fax cover page file.

What systems are primarily at risk from the vulnerability? 
Workstations and terminal servers are primarily at risk. Servers could be at more risk if administrators allow users to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do? 
The update addresses the vulnerability by correcting the manner in which the Windows Fax Page Editor parses fax cover page files.

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 CVE-2010-3974.

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 when this security bulletin was originally issued.

Does applying this security update help protect customers from the code, published publicly, that could attempt to exploit this vulnerability? 
Yes. This security update addresses the vulnerability that potentially could be exploited by using the published proof of concept code. The vulnerability that has been addressed has been assigned Common Vulnerability and Exposure number CVE-2010-3974.

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:

• On all supported editions of Windows XP and Windows Server 2003, the Windows Fax Cover Page Editor is not installed by default. For the Windows Fax Cover Page Editor to be available, the Fax Services component of these operating systems would need to be enabled.
• On all supported editions of Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2, by default, the affected file type (.cov) is not registered to any program. For an attack to be successful, a user would first need to open the Windows Fax Cover Page Editor and then open a specially crafted .cov file.
• The vulnerability cannot be exploited automatically through e-mail. For an attack to be successful, a user must open an attachment that is sent in an e-mail message.
• An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on 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 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 convince 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.

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:

• Remove the Fax Cover Page .COV file association on Windows XP and Windows Server 2003

  If the .cov file type has been associated with the Windows Fax Cover Page Editor, removing the file association prevents the file from being automatically opened.

  Note 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

  To remove the fax cover page (.cov) file association, perform the following steps:

  Using the interactive method

  1. Click Start, click Run, type regedit, and then click OK.
  2. Expand HKEY_CLASSES_ROOT, click on .COV, and then click the File menu and select Export.
  3. In the Export Registry File dialog box, type Cover_Page_Backup.reg and click Save.
     
     Note This will create a backup of this registry key in the My Documents folder by default.
  4. Press the Delete key on the keyboard to delete the registry key. When prompted to delete the registry value, click Yes.

  Using a managed deployment script

  1. Make a backup copy of the registry key using the following command:
     
     Regedit.exe /e cover_page_backup.reg HKEY_CLASSES_ROOT\.COV
  2. Save the following to a file with a .REG extension (e.g. Delete_Cover_Page_Assoc.reg):
     
     Windows Registry Editor Version 5.00

[-HKEY_CLASSES_ROOT\.COV]
  3. Run the registry script created in the previous step with the following command:
     
     Regedit.exe /s delete_cover_page.reg

  Impact of workaround. This workaround removes the .COV file association. Double-clicking a COV file will no longer launch Windows Fax Cover Page Editor.

  How to undo the workaround.

  Using the interactive method

  1. Click Start, click Run, type Regedit in the Open box, and then click OK.
  2. Click the File menu and select Import.
  3. In the Import Registry File dialog box, select Cover_Page_Backup.reg and click Open.

  Using a managed deployment script

  Restore the original state by running the following command:
  
  Regedit.exe /s cover_page_backup.reg

What is the scope of the vulnerability? 
This is a remote code execution vulnerability. 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.

What causes the vulnerability? 
The vulnerability is caused when the Windows Fax Cover Page Editor does not properly manage certain objects when parsing a specially crafted fax cover page.

What is the Windows Fax Cover Page Editor? 
The Fax Cover Page Editor (fxscover.exe) application can be used to create and edit fax cover pages.

In all supported editions of Windows XP and Windows Server 2003, the Windows Fax Cover Page Editor is only available if the optional Fax Services component is enabled. The Fax Services component is not installed by default on these operating systems. For information about enabling the Fax Services component of Microsoft Windows XP, see Microsoft Knowledge Base Article 306550.

In supported versions of Windows Vista Enterprise Edition, the Windows Fax Cover Page Editor is available as an optional component. In supported versions of Windows Vista Business Edition and Windows Vista Ultimate Edition, and in all supported editions of Windows 7, the Windows Fax Cover Page Editor is available by default. In supported versions of Windows Server 2008 (32-bit and x64-based only) and Windows Server 2008 R2 (x64-based only), the Fax Cover Page Editor is available if the Fax Server role is enabled. Typically, on these operating systems, the Windows Cover Page Editor is launched from within the Windows Fax and Scan application or from the Fax Service Manager when a user creates or edits a fax cover page. For more information on creating and editing fax cover pages, see Create or edit a fax cover page and the TechNet article, Managing Cover Pages.

What might an attacker use the vulnerability to do? 
An attacker who successfully exploited this vulnerability could run arbitrary code as the logged-on user. If a user is logged on with administrative user rights, an attacker could take complete control of the 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.

How could an attacker exploit the vulnerability? 
For an attacker to exploit this vulnerability, a user would need to open a specially crafted fax cover page file (.cov) using the Windows Fax Cover Page Editor.

In an e-mail attack scenario, an attacker could exploit the vulnerability by sending a specially crafted fax cover page file (.cov) to the user and by convincing the user to open the file within the Windows Fax Cover Page Editor application.

In a Web-based attack scenario, an attacker would have to host a Web site that contains a specially crafted fax cover page file (.cov) that is used to attempt to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site, and then convince them to open the specially crafted fax cover page file.

What systems are primarily at risk from the vulnerability? 
Workstations and terminal servers are primarily at risk. Servers could be at more risk if administrators allow users to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do? 
The update addresses the vulnerability by correcting the manner in which the Windows Fax Page Editor manages objects within fax cover page files.

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 CVE-2010-4701.

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 when this security bulletin was originally issued.

Does applying this security update help protect customers from the code, published publicly, that could attempt to exploit this vulnerability? 
Yes. This security update addresses the vulnerability that potentially could be exploited by using the published proof of concept code. The vulnerability that has been addressed has been assigned Common Vulnerability and Exposure number CVE-2010-4701.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Note For supported versions of Windows XP Professional x64 Edition, this security update is the same as supported versions of the Windows Server 2003 x64 Edition security update.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.