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AUSCERT External Security Bulletin Redistribution
ESB-2010.0411
Vulnerability in Microsoft SharePoint Could Allow Elevation of Privilege
30 April 2010
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AusCERT Security Bulletin Summary
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Product: Microsoft Office SharePoint Server 2007
Microsoft Windows SharePoint Services 3.0
Publisher: Microsoft
Operating System: Windows
Impact/Access: Increased Privileges -- Existing Account
Resolution: Mitigation
Original Bulletin:
http://www.microsoft.com/technet/security/advisory/983438.mspx
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Microsoft Security Advisory (983438)
Vulnerability in Microsoft SharePoint Could Allow Elevation of Privilege
Published: April 29, 2010
Version: 1.0
General Information
Executive Summary
Microsoft is investigating new public reports of a possible vulnerability in
Microsoft Windows SharePoint Services 3.0 and Microsoft Office SharePoint
Server 2007. The vulnerability could allow an attacker to run arbitrary script
that could result in elevation of privilege within the SharePoint site, as
opposed to elevation of privilege within the workstation or server
environment.
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
Microsoft Office SharePoint Server 2007 Service Pack 1 and Microsoft Office
SharePoint Server 2007 Service Pack 2 (32-bit editions)
Microsoft Office SharePoint Server 2007 Service Pack 1 and Microsoft Office
SharePoint Server 2007 Service Pack 2 (64-bit editions)
Microsoft Windows SharePoint Services 3.0 Service Pack 1 and Microsoft Windows
SharePoint Services 3.0 Service Pack 2 (32-bit editions)
Microsoft Windows SharePoint Services 3.0 Service Pack 1 and Microsoft Windows
SharePoint Services 3.0 Service Pack 2 (64-bit editions)
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:
An attacker can cause arbitrary JavaScript to be run by the user clicking the
specially crafted URL, but the attacker would not be able to steal the
logged-on user's authentication credentials due to the way SharePoint Server
handles the HttpOnly authentication cookie
The vulnerability cannot be exploited automatically through e-mail. For an
attack to be successful, a user must click on a URL that is sent in an e-mail
message.
Internet Explorer 8 users browsing to a SharePoint site in the Internet Zone
are at a reduced risk because, by default, the XSS Filter in Internet Explorer
8 prevents this attack in the Internet Zone. The Internet Explorer 8 XSS
Filter, however, is not enabled by default in the Intranet Zone.
Suggested Actions
Customers can mitigate the impact to systems running Microsoft Windows
SharePoint Services 3.0 or Microsoft Office SharePoint Server 2007 by applying
the following workarounds.
Workaround refers to a setting or configuration change that does not correct
the underlying issue 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:
Restrict Access to SharePoint Help.aspx
An administrator can apply an access control list to SharePoint Help.aspx to
ensure that they can no longer be loaded. This effectively prevents
exploitation of the vulnerability using this attack vector.
To restrict access to the vulnerable Help.aspx:
Run the following commands from a command prompt:
cacls "%ProgramFiles%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx" /E /P everyone:N
cacls "%ProgramFiles(x86)%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx" /E /P everyone:N
Impact of workaround. This workaround will disable all help functionality from
the SharePoint server.
How to undo the workaround.
Run the following commands from a command prompt:
takeown /f "%ProgramFiles%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx"
takeown /f "%ProgramFiles(x86)%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx"
cacls "%ProgramFiles%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx" /E /R everyone
cacls "%ProgramFiles(x86)%\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\Help.aspx" /E /R everyone
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