Public Vulnerability Reports

ClamAV libclamav PE File Integer Overflow Vulnerability

02.12.08

BACKGROUND

Clam AntiVirus is a multi-platform GPL anti-virus toolkit. ClamAV is often integrated into e-mail gateways and used to scan e-mail traffic for viruses. It supports virus scanning for a wide variety of packed Portable Executable (PE) binaries. For more information visit the vendor's web site at the following URL.

http://www.clamav.net/

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 and scanning PE files. While iterating through all sections contained in the PE file, several attacker controlled values are extracted from the file. On each iteration, arithmetic operations are performed without taking into consideration 32-bit integer wrap.

Since insufficient integer overflow checks are present, an attacker can cause a heap overflow by causing a specially crafted Petite packed PE binary to be scanned. This results in an exploitable memory corruption condition.

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.

Address Space Layout Randomization (ASLR) and non-executable memory protection technologies (such as DEP, NX, XD, PaX, etc) can help mitigate exploitation of this type of vulnerability.

DETECTION

iDefense has confirmed the existence of this vulnerability in ClamAV 0.92. Previous versions may also be affected.

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'.

VENDOR RESPONSE

The ClamAV team has addressed this vulnerability within version 0.92.1. Additionally, the ClamAV team reports, "the vulnerable module was remotely disabled via virus-db update on Jan 11th 2008."

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-0318 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

01/07/2008 Initial vendor notification
01/11/2008 Initial vendor response
02/12/2008 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by Silvio Cesare.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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