Date: 11 June 2010
References: ASB-2010.0254 ASB-2011.0109
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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
Operating System: Windows XP
Windows Server 2003
Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction
CVE Names: CVE-2010-1885
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Microsoft Security Advisory (2219475)
Vulnerability in Windows Help and Support Center Could Allow Remote Code Execution
Published: June 10, 2010
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.
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
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
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,
* 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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