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Kaspersky AntiVirus UPX File Decompression DoS Vulnerability
iDefense Security Advisory 03.02.07: Kaspersky AntiVirus UPX File Decompression DoS Vulnerability
iDefense Security Advisory 03.02.07: Kaspersky AntiVirus UPX File Decompression DoS Vulnerability

Kaspersky AntiVirus UPX File Decompression DoS Vulnerability

iDefense Security Advisory 03.02.07 
Mar 02, 2007


Kaspersky Antivirus is a popular client and gateway virus scanner for Unix
and Windows. UPX, the ultimate packer for executables, is a method for
compressing executable files to reduce their size on disk. For more
information, visit the vendor's site at the following URL. 


Remote exploitation of a denial of service (DoS) vulnerability in Kaspersky
Lab's Antivirus could allow an attacker to conduct a DoS attack on a
targeted host.

The antivirus engine is vulnerable to a DoS condition when processing an
executable packed with UPX compression. Malformed compressed data causes
the decompression routine to enter an infinite loop. Specifically, a
negative data offset results in the same compressed data chunk being
processed endlessly.


Exploitation allows an attacker to conduct a DoS attack.

If this attack is conducted against an e-mail gateway running Kaspersky,
legitimate clients may be unable to send e-mail through the server.

The infinite loop being executed consists of a short sequence of
instructions, which results in maximum CPU usage. On a client desktop, the
infinite loop will render the machine nearly unusable. On a server, it
severely degrades the quality of service of other applications running.


iDefense has confirmed the existence of this vulnerability in Kaspersky
Labs Antivirus Engine version for Windows and 5.5-10 for Linux.
Previous versions may also be affected. Any products that use the scanning
engine are also affected, which includes the Kaspersky e-mail gateway


iDefense is currently unaware of any workarounds for this issue.


Kaspersky Lab reports that it has fixed this vulnerability as of February
7th, 2007. In addition, they stated the following.

"There is no need to download any special patches. All installed Kaspersky
Lab products are updated automatically through the regular signature-update
functionality. There is not need to contact Kaspersky Lab to obtain this


A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.


01/24/2007  Initial vendor notification
03/01/2007  Initial vendor response
03/02/2007  Coordinated public disclosure


The discoverer of this vulnerability wishes to remain anonymous.

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Copyright =A9 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 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

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