[TZO-40-2009] Clamav generic bypass (RAR,CAB,ZIP)

From: Thierry Zoller <Thierry@Zoller.lu>
To: bugtraq <bugtraq@securityfocus.com>,info@circl.etat.lu,vuln@secunia.com,cert@cert.org,nvd@nist.gov,cve@mitre.org,full-disclosure@lists.grok.org.uk
Subject: [TZO-40-2009] Clamav generic bypass (RAR,CAB,ZIP)


                From the low-hanging-fruit-department
                   Clamav generic evasion (RAR,CAB,ZIP)

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Release mode: Coordinated but limited disclosure.
Ref         : [TZO-40-2009] - Clamav generic evasion (RAR,CAB,ZIP)
WWW         : http://blog.zoller.lu/2009/05/advisory-clamav-generic-bypass.html
Vendor      : http://www.clamav.net &
Status      : Patched (in version 0.95.2)
CVE         : none provided
Credit      : Discovered - froggz 2005, Zoller 2007, ROGER Mickael 2009
Security notification reaction rating : good

Disclosure Policy : 

Affected products : 
- ClamAV below 0.95.2

Affected systems:
- MACOSX server,
- IBM Secure E-mail Express Solution for System

I. Background
Quote: "Clam AntiVirus is an open source (GPL) anti-virus toolkit for UNIX, 
designed especially for e-mail scanning on mail gateways. It provides 
a number of utilities including a flexible and scalable multi-threaded
daemon, a command line scanner and advanced tool for automatic 
database updates. The core of the package is an anti-virus engine 
available in a form of shared library. "

II. Description
The parsing engine can be bypassed by manipulating RAR,ZIP archives 
in a "certain way" that the Clamav engine cannot extract the content but
the end user is able to. 

III. Impact
To know more about the impact and type of "evasion", I updated the 
description at http://blog.zoller.lu/2009/04/case-for-av-bypassesevasions.html

IV. Disclosure timeline

No timeline, nothing particular to note.

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