iDefense Security Advisory 02.12.08: Microsoft Office Works Converter Stack-based Buffer Overflow Vulnerability

iDefense Security Advisory 02.12.08
http://labs.idefense.com/intelligence/vulnerabilities/
Feb 12, 2008

I. 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/

II. 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.

III. 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.

IV. 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.

V. 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.

VI. 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

VII. 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.

VIII. DISCLOSURE TIMELINE

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

IX. CREDIT

This vulnerability was reported to VeriSign iDefense by sillypea.

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X. LEGAL NOTICES

Copyright © 2008 iDefense, 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.