iDefense Security Advisory 10.13.09
http://labs.idefense.com/intelligence/vulnerabilities/
Oct 13, 2009

I. BACKGROUND

Microsoft Office is a suite of products used for document, spreadsheet,
and presentation creation and viewing. Office Drawing Format is a
binary file format developed by Microsoft. It is used by all Office
programs to represent information about different types of shapes and
drawings commonly used in Office applications. For more information see
the vendor's website.

http://office.microsoft.com/

II. DESCRIPTION

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

The vulnerability occurs when parsing the msofbtOPT Office Drawing
record type. This record is used to provide default values for shape
properties. By inserting a specially crafted property ID, it is
possible to corrupt heap memory and overwrite an object pointer.

III. 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. After opening the file, no further interaction is needed to
trigger the vulnerability.

Due to the nature of the vulnerability, it is possible to reliably
overwrite an object pointer. This lets an attacker control the object's
virtual function table, which simplifies exploitation.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in Office XP
SP3.

V. WORKAROUND

The vulnerability occurs in the core parsing code, and this code can not
be disabled; however, it is possible to disable the opening of the older
binary format files and use MOICE to convert the file to the newer
XML-based format.

VI. VENDOR RESPONSE

Microsoft has released a patch which addresses this issue. For more
information, consult their advisory at the following URL:

http://www.microsoft.com/technet/security/Bulletin/MS09-062.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-2528 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

04/25/2008  - Initial Contact
04/25/2008  - Initial Response
04/25/2008  - PoC Requested
07/21/2008  - PoC Requested
07/21/2008  - PoC Sent
12/11/2008  - Status Update Received - no estimated release date
02/19/2009  - Status Update Received - new case manager, estimated
release date 06/09/2009
10/13/2009  - Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Marsu and an anonymous
contributor.

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X. LEGAL NOTICES

Copyright © 2009 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
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