Microsoft OLE CPropertyStorage::ReadMultiple Variant Type Confusion Vulnerability
12.13.11
BACKGROUND

Many Windows applications that support the structured storage file format (Office applications for example) contain support for reading the SummaryInformation stream inside of the OLE document. This stream contains various properties that describe the document (the author for example). In addition to Office, Windows Explorer also supports parsing these streams when a file is clicked and viewed via the preview pane.
DESCRIPTION

Remote exploitation of a type confusion vulnerability in Microsoft Corp.'s Windows could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability occurs in the 'CPropertyStorage::ReadMultiple' function. It is triggered when trying to convert a property in the property set to a variant type. Specifically, a type confusion occurs when a string property is treated as a certain variant. This results in the first 4 bytes of the string being treated as a VTABLE pointer, which can lead to the execution of arbitrary code.
ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user opening the file. To exploit this vulnerability, an attacker needs to convince a user to open a malicious file. Attackers typically accomplish this by e-mailing a targeted user the file or hosting the file on a Web page. Additionally, this vulnerability can be triggered if a user previews the file in Explorer. This can be accomplished by clicking on the file in its folder.
DETECTION

The following Microsoft products are vulnerable:

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

WORKAROUND

iDefense is currently unaware of any workaround for this issue.
VENDOR RESPONSE

Microsoft has released updates to address this vulnerability. For more information, consult their advisory at the following URL.

http://technet.microsoft.com/en-us/security/bulletin/ms11-093
CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2011-3400 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.
DISCLOSURE TIMELINE

08/10/2011 Initial Vendor Notification
08/10/2011 Initial Vendor Reply
12/13/2011 Coordinated Public Disclosure
CREDIT

This vulnerability was reported to iDefense by Luigi Auriemma.

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