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Category:   Application (Security)  >   Clam AntiVirus Vendors:
Clam AntiVirus CAB File Descriptor Leak Lets Remote Users Deny Service
SecurityTracker Alert ID:  1017659
SecurityTracker URL:
CVE Reference:   CVE-2007-0897   (Links to External Site)
Date:  Feb 16 2007
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 0.90 stable
Description:   A vulnerability was reported in Clam AntiVirus. A remote user can cause denial of service conditions.

A remote user can send a CAB archive with a specially crafted cabinet file header to trigger a file descriptor leak and cause the target service to consume all available file descriptors. As a result, the anti-virus software will fail to subsequently scan most archives.

The vendor was notified on February 7, 2007.

iDefense reported this vulnerability.

Impact:   A remote user can cause denial of service conditions.
Solution:   The vendor has issued a fixed version (0.90 stable).
Vendor URL: (Links to External Site)
Cause:   Resource error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   None.

 Source Message Contents

Subject:  iDefense Security Advisory 02.15.07: Multiple Vendor ClamAV CAB File

Multiple Vendor ClamAV CAB File Denial of Service Vulnerability

iDefense Security Advisory 02.15.07
Feb 15, 2007


Clam AntiVirus is a multi-platform GPL anti-virus toolkit. The main purpose
of which is integration into electronic mail servers. More information
about ClamAV can be found at Microsoft CAB files are
the native compressed file format for Windows.


Remote exploitation of a resource consumption vulnerability in Clam
AntiVirus' ClamAV allows attackers to degrade the service of the clamd

The vulnerability specifically exists due to a file descriptor leak.  When
clam encounters a cabinet header with a record length of zero it will
return from a function without closing a local file descriptor. This can
be triggered multiple times, eventually using up all but three of its
available file descriptors. This prevents clam from scanning most
archives, including zip and tar files.


Exploitation allows attackers to degrade the functionality of the ClamAV
virus scanning service. Exploitation requires that attackers send a
specially constructed CAB file through an e-mail gateway or personal
anti-virus client using the ClamAV scanning engine.

When ClamAV is unable to scan an archive successfully because it has run
out of descriptors, it will return an error status. Several mail servers
that use clam were tested to see how they handled this status. Exim, as of
version 4.50, features an option to build clamd support into it. It will
reject a mail if clamd fails to scan it properly. Amavisd will also deny a
mail that clamd cannot properly scan. This vulnerability can be used to
deny service to users trying to send legitimate archives through the mail


iDefense has confirmed this vulnerability affects Clam AntiVirus ClamAV
v0.90RC1.1. All versions prior to the 0.90 stable release are suspected
to be


iDefense is unaware of any effective workarounds for this issue.


Clam AntiVirus has addressed this vulnerability in the version 0.90 stable


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0897 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


02/07/2007  Initial vendor notification
02/13/2007  Initial vendor response
02/15/2007  Coordinated public disclosure


The discoverer of this vulnerability wishes to remain anonymous.

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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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