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             AUSCERT External Security Bulletin Redistribution

          Vulnerability in Windows Help and  Support Center Could
                        Allow Remote Code Execution
                               11 June 2010


        AusCERT Security Bulletin Summary

Product:           Windows Help and Support Center
Publisher:         Microsoft
Operating System:  Windows XP
                   Windows Server 2003
Impact/Access:     Execute Arbitrary Code/Commands -- Remote with User Interaction
Resolution:        Mitigation
CVE Names:         CVE-2010-1885  

Original Bulletin: 

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Microsoft Security Advisory (2219475)

Vulnerability in Windows Help and  Support Center Could Allow Remote Code Execution

Published: June 10, 2010

Version: 1.0 

General Information

Executive Summary

  Microsoft is investigating new public reports of a possible vulnerability in 
  the Windows Help and Support Center function that is delivered with supported
  editions of Windows XP and Windows Server 2003. This vulnerability could allow
  remote code execution if a user views a specially crafted Web page using a Web
  browser or clicks a specially crafted link in an e-mail message. Microsoft is
  aware that proof of concept exploit code has been published for the 
  vulnerability. However, Microsoft is not currently aware of active attacks 
  that use this exploit code or of customer impact at this time. Microsoft is 
  actively monitoring this situation to keep customers informed and to provide 
  customer guidance as necessary.

  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.

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

Affected Software

  Windows XP Service Pack 2 and Windows XP Service Pack 3
  Windows XP Professional x64 Edition Service Pack 2
  Windows Server 2003 Service Pack 2
  Windows Server 2003 x64 Edition Service Pack 2
  Windows Server 2003 with SP2 for Itanium-based Systems

Mitigating Factors

  Mitigation refers to a setting, common configuration, or general best-practice,
  existing in a default state, that could reduce the severity of this issue.
  The following mitigating factors may be helpful in your situation:
  * 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.
  * The vulnerability cannot be exploited automatically through e-mail. For an
    attack to be successful a user must click a link listed within an e-mail
  * 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.


  Workaround refers 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. Microsoft has tested the following workarounds
  and states in the discussion whether a workaround reduces functionality:
  * Unregister the HCP Protocol

    Note Using Registry Editor incorrectly can cause serious problems that may
    require you to reinstall your operating system. Microsoft cannot guarantee
    that problems resulting from the incorrect use of Registry Editor can be
    solved. Use 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.

    Unregistering the HCP Protocol prevents this issue from being exploited on
    affected systems.

    Using the Interactive Method

    1. Click Start, click Run, type Regedit in the Open box, and then click OK

    2. Locate and then click the following registry key:


    3. Click the File menu and select Export

    4. In the Export Registry File dialog box, enter HCP_Procotol_Backup.reg
       and click Save.

       Note This will create a backup of this registry key in the My Documents
       folder by default.

    5. Press the Delete key on the keyboard to delete the registry key. When
       prompted to delete the registry key via the Confirm Key Delete dialog box,
       click Yes.

  * Using a Managed Deployment Script

    1. Create a backup copy of the registry keys by using a managed deployment
       script that contains the following commands:

       Regedit.exe /e HCP_Protocol_Backup.reg HKEY_CLASSES_ROOT\HCP

    2. Next, save the following to a file with a .REG extension, such as

       Windows Registry Editor Version 5.00


    3. Run the above registry script on the target machine with the following
       command from an elevated command prompt:

       Regedit.exe /s Disable_HCP_Protocol.reg

  Impact of Workaround: Unregistering the HCP protocol will break all local,
  legitimate help links that use hcp://. For example, links in Control Panel may
  no longer work.

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 HCP_Procotol_Backup.reg
       and click Open.

  * Using a Managed Deployment Script
     Restore the original state by running the following command:

     Regedit.exe /s HCP_Protocol_Backup.reg

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