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Sophos Antivirus CHM File Heap Overflow Vulnerability

12.08.06

BACKGROUND

Sophos AntiVirus offers protection from the latest Trojans, worms and Viruses. More information is available on the vendors site at:

http://sophos.com/products/

DESCRIPTION

Sophos AntiVirus Engine is vulnerable to a Heap Overflow attack when scanning malformed CHM archives.

Specifically, if the CHM file has a Window_size of 0 set in a LZX decompression header then memory corruption will occur.

ANALYSIS

Malformed CHM files can lead to a heap overflow condition on the local machine. Files received as email attachments, uploaded via web forms or otherwise saved to disk may trigger this condition if auto scanning is enabled on the target machine. Archive scanning is disabled by default and must be specified in order for this vulnerability to trigger.

DETECTION

iDefense has confirmed this vulnerability in the following Sophos Antivirus products:

  • Sophos Antivirus for Linux
    Product version: 4.03
    Engine version : 4.05

Previous versions of Sophos Antivirus are suspected vulnerable. Other Sophos Antivirus products may also be vulnerable.

Windows versions of the Sophos Antivirus product do not appear to be vulnerable.

WORKAROUND

Disabling the option to scan within archives will prevent exploitation of this vulnerability.

VENDOR RESPONSE

Sophos has addressed this problem with new versions of their products. See http://www.sophos.com/support/knowledgebase/article/7609.html for more information.

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-5646 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

09/28/2006 Initial vendor notification
10/02/2006 Initial vendor response
12/08/2006 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by Damian Put <pucik@overflow.pl>.

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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.