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Category:   Application (Security)  >   Clam AntiVirus Vendors:   clamav.sourceforge.net
Clam AntiVirus Integer Overflow in Processing MEW Packed Files Lets Remote Users Execute Arbitrary Code
SecurityTracker Alert ID:  1019112
SecurityTracker URL:  http://securitytracker.com/id/1019112
CVE Reference:   CVE-2007-6335   (Links to External Site)
Updated:  Dec 20 2007
Original Entry Date:  Dec 18 2007
Impact:   Execution of arbitrary code via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 0.92
Description:   A vulnerability was reported in Clam AntiVirus. A remote user can cause arbitrary code to be executed on the target user's system.

A remote user can create a specially crafted PE file packed with the MEW packer that, when processed by the target application, will trigger an integer overflow and execute arbitrary code on the target system. The code will run with the privileges of the target application.

The vendor was notified on October 17, 2007.

iDefense reported this vulnerability.

Impact:   A remote user can create a file that, when processed by the target user or application, will execute arbitrary code on the target system.
Solution:   The vendor has issued a fixed version (0.92).

The ClamAV advisory is available at:

http://svn.clamav.net/svn/clamav-devel/trunk/ChangeLog

Vendor URL:  www.clamav.net/ (Links to External Site)
Cause:   Boundary error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   None.


 Source Message Contents

Subject:  iDefense Security Advisory 12.18.07: ClamAV libclamav MEW PE File

iDefense Security Advisory 12.18.07
http://labs.idefense.com/intelligence/vulnerabilities/
Dec 18, 2007

I. BACKGROUND

Clam AntiVirus is a multi-platform anti-virus toolkit released under the
GNU Public License. ClamAV is often integrated into e-mail gateways and
used to scan e-mail messages for viruses. PE, or portable executable,
is the executable file format on Microsoft Windows systems. MEW is one
of the many executable packers that is supported by ClamAV. More
information can be found on the vendor's website at the following URL.

http://www.clamav.net/

II. DESCRIPTION

Remote exploitation of an integer overflow vulnerability in Clam
AntiVirus' ClamAV, as included in various vendors' operating system
distributions, allows attackers to execute arbitrary code with the
privileges of the affected process.

The vulnerability exists within the code responsible for parsing PE
files packed with the MEW packer. During unpacking, two untrusted
values are taken directly from the file without being validated. These
values are later used in an arithmetic operation to calculate the size
used to allocate a heap buffer. This calculation can overflow,
resulting in a buffer of insufficient size being allocated. This later
leads to arbitrary areas of memory being overwritten with attacker
supplied data.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the process using libclamav.

In the case of the clamd program, this will result in code execution
with the privileges of the clamav user. Unsuccessful exploitation
results in the clamd process crashing.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in ClamAV
0.91.2. Previous versions may also be affected.

V. WORKAROUND

Disabling the scanning of PE files will prevent exploitation. If using
clamscan, this can be done by running clamscan with the '--no-pe'
option. If using clamdscan, set the 'ScanPE' option in the clamd.conf
file to 'no'.

VI. VENDOR RESPONSE

The ClamAV team has addressed this vulnerability within version 0.92.

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-5759 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

10/17/2007  Initial vendor notification
10/18/2007  Initial vendor response
12/18/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php

Free tools, research and upcoming events
http://labs.idefense.com/

X. LEGAL NOTICES


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 customerservice@idefense.com 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.

 
 


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