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Microsoft Excel Long Palette Heap Overflow Vulnerability

01.09.07

BACKGROUND

Microsoft Excel is the spreadsheet application from the Microsoft Office System. More information is available at the following link:

http://office.microsoft.com/

DESCRIPTION

Remote exploitation of an heap-based buffer overflow vulnerability in Microsoft Corp.'s Excel spreadsheet application format could allow an attacker to execute arbitrary code in the context of the user who started Excel.

The vulnerability specifically exists in the handling of the PALETTE record in BIFF8 format spreadsheet files. By supplying a record with too many entries, an exploitable buffer overflow condition can occur.

ANALYSIS

Successful exploitation of this vulnerability would allow an attacker to execute arbitrary code in the context of the user who opened the document. In order exploit this vulnerability, an attacker would need to convince the target to open an Excel spreadsheet file. Likely attack vectors include sending the file as an attachment in an email or linking to the file on a website.

Systems with a default install of Office 2000 will open Office documents, including Excel spreadsheet files, from websites without prompting the user. This allows an attacker to exploit this vulnerability without user interaction beyond visiting a website. Later versions of Office will not open these documents automatically unless the user has chosen this behavior.

DETECTION

iDefense Labs have confirmed the existence of this vulnerability in Microsoft Excel 2003 with all service packs and security updates. Previous versions of Excel are also likely to be affected.

WORKAROUND

Do not follow links or open files from unknown sources or that you were not expecting to receive.

VENDOR RESPONSE

Microsoft has addressed this vulnerability with Microsoft Security Bulletin MS07-002. A link to this bulletin can be found below.

http://www.microsoft.com/technet/security/bulletin/ms07-002.mspx

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-0031 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

09/22/2006 Initial vendor notification
09/22/2006 Initial vendor response
01/09/2007 Coordinated public disclosure

CREDIT

This vulnerability was discovered by Greg MacManus, iDefense Labs.

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LEGAL NOTICES

Copyright © 2006 Verisign, Inc.

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 customer service 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.