iDefense Security Advisory 09.13.11
http://labs.idefense.com/intelligence/vulnerabilities/
Sep 13, 2011

I. BACKGROUND

Excel is the spreadsheet application included with Microsoft Corp.'s
Office productivity software suite. More information is available at the
following website:

http://office.microsoft.com/excel/

II. DESCRIPTION

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

The vulnerability occurs when Excel parses a certain specially crafted
record in an Excel file. An invalid value of the length field in the
record header can trigger an error condition and result in using memory
content which has already been freed and may allow arbitrary code
execution.

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. Attackers typically accomplish this by e-mailing a targeted user
the file or hosting the file on a Web page.

IV. DETECTION

Microsoft has reported the following products vulnerable:

    * Microsoft Excel 2003 SP 3
    * Microsoft Excel 2007 SP 2
    * Microsoft Office 2007 SP 2
    * Microsoft Excel 2010 (32-bit editions)
    * Microsoft Excel 2010 SP 1 (32-bit editions)
    * Microsoft Office 2010 and Microsoft Office 2010 SP 1 (32-bit editions)
    * Microsoft Excel 2010 (64-bit editions)
    * Microsoft Excel 2010 SP 1 (64-bit editions)
    * Microsoft Office 2010 and Microsoft Office 2010 SP 1 (64-bit editions)
    * Microsoft Office 2004 for Mac
    * Microsoft Office 2008 for Mac
    * Microsoft Office for Mac 2011
    * Open XML File Format Converter for Mac
    * Microsoft Excel Viewer SP 2
    * Microsoft Office Compatibility Pack for Word, Excel, and
PowerPoint 2007 File Formats SP 2
    * Excel Services
    * Microsoft Excel Web App 2010 and Microsoft Excel Web App 2010 SP 1

V. WORKAROUND

Microsoft suggested workarounds can be found under the Workaround
section within Microsoft Security Bulletin MS11-072.

http://technet.microsoft.com/en-us/security/bulletin/ms11-072

VI. VENDOR RESPONSE

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

http://technet.microsoft.com/en-us/security/bulletin/ms11-072

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2011-1986 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

02/16/2011  Initial Vendor Notification
02/16/2011  Vendor Reply
09/13/2011  Coordinated Public Disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php

Free tools, research and upcoming events
http://labs.idefense.com/

X. LEGAL NOTICES

Copyright © 2011 Verisign

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDefense. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
e-mail customerservice@idefense.com for permission.

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.