I. BACKGROUND
AntiVirus products typically handle searching files for known viruses
within their scan engines. Most scan engines support searching inside
of known archive types for viruses as well. For more information refer
to any of the popular AntiVirus vendors' web sites.
II. DESCRIPTION
Remote exploitation of a denial of service vulnerability in Multiple
Vendors' Antivirus engines allows an attacker to cause the engines to
consume excessive resources.
The affected vendors' scan engines are vulnerable to a DoS attack when
scanning malformed RAR archives. Specifically, the malformed archives
will have the head_size and pack_size fields set to zero in the Archive
Header section. When such a file is encountered, the affected scan
engines will enter an infinite loop.
III. ANALYSIS
Exploitation allows an attacker to cause the affected scan engine to
consume excessive CPU or memory resources. The malicious RAR file would
need to be uploaded to a server to initiate the attack. Several common
ways this could be achieved include; e-mail attachments, available
network shares, FTP accounts, or Web form uploads.
The impact of the vulnerability varies slightly from vendor to vendor as
described below.
Sophos:
Scanning of archives is not enabled by default and must be specified by
the user. This denial of service attack will prevent the scanner from
scanning other files on disk while it is stuck on the exploit file. The
hung process can be stopped by the user.
Computer Associates:
This denial of service attack will prevent the scanner from scanning
other files on disk while it is stuck on the exploit file. The hung
process can be quit by the user and does not consume all system
resources.
Trend Micro:
Once attacked, the scan engine will consume 99 percent of CPU resources
and the affected computer will require a reboot to recover from the
condition. The scan engine process cannot be forced to quit, although
its thread priority can be lowered to regain some use of the system
before reboot.
IV. DETECTION
iDefense has confirmed this vulnerability exists in the following
vendors' products. This should not be considered an exhaustive list as
these vendors tend to include the scan engine in many of their
products. Previous versions are likely to be affected as well.
- Sophos Small business edition (Windows/Linux) 4.06.1 with engine version 2.34.3.
- Computer Associates eTrust Antivirus v7.1.8.0 (A/V engine version 12.4.1)
- Trend Micro PC Cillin - Internet Security 2006
- Trend Micro Office Scan 7.3
- Trend Micro Server Protect 5.58
V. WORKAROUND
For Sophos' scan engine, this exploit will not have any effect if the
"Enabled scanning of archives" option is not set. iDefense is currently
unaware of a workaround for this issue for the remaining vendor's
engines.
VI. 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.
Trend Micro stated that this vulnerability does not affect version 8.320
of their Windows scan engine. Additionally, they have released version
8.150 of the HPUX and AIX builds of their scan engine to address this
problem in those environments.
Computer Associates has addressed this vulnerability by releasing
updates. These updates are available via the products' automatic update
features. More information is available within Computer Associates'
advisory at the following URL.
http://supportconnectw.ca.com/public/antivirus/infodocs/caprodarclib-s
ecnot.asp
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2006-5645 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
09/27/2006 Initial vendor notifications
09/27/2006 Initial vendor response - Trend Micro
09/27/2006 Initial vendor response - Computer Associates
09/28/2006 Initial vendor response - Sophos
12/08/2006 Coordinated public disclosure
07/24/2007 Coordinated public disclosure - Computer Associates
IX. CREDIT
This vulnerability was reported by Titon of BastardLabs, Damian Put
<,">pucik@overflow.pl>, and an anonymous researcher.
Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php
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http://labs.idefense.com/
X. LEGAL NOTICES
Copyright © 2007 iDefense, 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.
