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Microsoft Office Works Converter Stack-based Buffer Overflow Vulnerability

02.12.08

BACKGROUND

Microsoft Word is a word processing application which is heavily used in corporate environments. Word comes with Office Converters that allow it to import files from various formats such as old versions of other word processing software. More information can be found on the vendor's site at the following URL.

http://office.microsoft.com/

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in Microsoft Corp.'s Works Converter allows attackers to execute arbitrary code as the current user.

This vulnerability stems from improper input validation of section length headers when converting a Microsoft Works document (WPS extension) to Rich Text Format (RTF). When certain fields are modified, such as the length or count values, a stack-based buffer overflow occurs. This leads to a directly exploitable condition.

ANALYSIS

Exploitation allows attackers to execute arbitrary code as the user that converts a specially crafted Works document.

Exploitation might require the installation of additional Microsoft Office components. When installing Microsoft Office, there are several installation options for converters. In corporate environments, the required components are usually set to be installed from the hard drive on first use. However, one of the installation options causes a request for the installation media. If this option is used, the media prompt may help mitigate exploitation.

In order to exploit this vulnerability, the targeted user must manually choose to open the malformed Works document in Microsoft Word. The file extension is not registered by default.

DETECTION

iDefense confirmed that wkcvqd01.dll version 7.03.0616.0, as included with Microsoft Office 2003, is vulnerable. Older versions of Microsoft Office as well as Microsoft Works are also assumed vulnerable.

WORKAROUND

User awareness is the best defense against this type of attack. Users should not open attachments or click URLs from untrusted or unknown sources.

VENDOR RESPONSE

Microsoft has officially addressed this vulnerability with Security Bulletin MS08-011. For more information, consult their bulletin at the following URL.

http://www.microsoft.com/technet/security/Bulletin/ms08-011.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-0108 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

06/14/2007 Initial vendor notification
06/14/2007 Initial vendor response
02/12/2008 Coordinated public disclosure

CREDIT

This vulnerability was reported to VeriSign iDefense by sillypea.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.