Public Vulnerability Reports

Microsoft Word FIB Processing Stack Buffer Overflow Vulnerability



Microsoft Word is a word processing application that is part of the Microsoft Office suite of products. For more information about Microsoft Word, see following website.


Remote exploitation of a stack buffer overflow vulnerability in Microsoft Corp.'s Word could allow attackers to execute arbitrary code with the privileges of the targeted user.

This vulnerability occurs when Word parses the File Information Block (FIB) structure inside a Word document. When a malformed FIB structure is processed, a stack buffer overflow will occur which can lead to an exploitable condition.


Exploitation allows remote attackers to execute arbitrary code on the affected host under the context of the user opening the file.

Exploitation might require that the user open a specially crafted word document with a vulnerable application. The most likely exploitation vector involves convincing a user to open a word document sent to them via e-mail or linked on a website.


iDefense has confirmed fully patched Microsoft Word 2003 SP3, Microsoft Word XP SP3, Microsoft Word 2000 SP3 are vulnerable.

Microsoft Word 2007 SP1 is not affected.


iDefense is currently unaware of any effective workaround for this issue. Since the vulnerability occurs in the core parsing code, it is not possible to disable the affected module.

User awareness is the best defense against this type of attack. Users should not follow links or open attachments from untrusted sources or that are received unexpectedly from trusted sources.


Microsoft Corp. has released a patch which addresses this issue. Information about downloadable vendor updates can be found by clicking on the URLs shown.


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2009-3135 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


03/06/2009 - Initial Contact
03/07/2009 - Initial Response
05/21/2009 - Tentative disclosure set for September
06/25/2009 - Requested CVE from Vendor
11/10/2009 - Coordinated Public Disclosure


This vulnerability was discovered by Jun Mao, iDefense Labs.

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Copyright © 2009 Verisign, Inc.

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