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

From: Thierry Zoller (ThierryZoller.lu)
Date: Tue Jun 16 2009 - 06:13:19 CDT


________________________________________________________________________

                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 &
              http://www.sourcefire.com/products/clamav
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 :
http://blog.zoller.lu/2008/09/notification-and-disclosure-policy.html

Affected products :
- ClamAV below 0.95.2

Affected systems:
- MACOSX server,
- IBM Secure E-mail Express Solution for System
http://www.clamav.net/about/who-use-clamav/

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
~~~~~~~~~~~~~~~~~~~~~~~~~
DD/MM/YYYY

No timeline, nothing particular to note.

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