Vulnerability Note VU#858595

ClamAV upack heap buffer overflow vulnerability

Overview

The ClamAV anti-virus scanner contains a vulnerability that may allow an attacker to execute code or cause ClamAV to crash.

I. Description

The Portable Executable (PE) file format is a file format for executable files that is used in Microsoft Windows. PE files can be packed with executable packers, such as upack. The ClamAV anti-virus scanner can unpack and scan PE files that are packed with upack.

From ClamAV bug ID 878:

Secunia Research has discovered a vulnerability in ClamAV, which can be exploited by malicious people to compromise a vulnerable system.

The vulnerability is caused due to a boundary error within the "cli_scanpe()" function in libclamav/pe.c. This can be exploited to cause a heap-based buffer overflow via a specially crafted "Upack" executable.

Note that the ClamAV team has disabled the scanning of PE files that were packed with upack in older versions of ClamAV to prevent this vulnerability from being exploited.

II. Impact

A remote, unauthenticated attacker may be able to execute arbitrary code or cause ClamAV to crash.

III. Solution

Upgrade

Users are encouraged to upgrade to ClamAV .93, which was released to address this issue. Note that because of a workaround applied by the ClamAV team, ClamAV versions prior to .93 may not be able to scan PE files that were packed with the upack packer.

Do not run clamscan as root

To limit the impact of vulnerabilities in ClamAV, users and administrators should run clamscan with a limited user account.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Clam AntiVirus	Vulnerable	18-Apr-2008

References

https://www.clamav.net/bugzilla/show_bug.cgi?id=878
http://secunia.com/secunia_research/2008-11/
http://en.wikipedia.org/wiki/Portable_Executable
http://www.microsoft.com/whdc/system/platform/firmware/PECOFF.mspx
http://linux.die.net/man/1/clamscan

Credit

Thanks to Secunia Research and the ClamAV team for information that was used in this report.

This document was written by Ryan Giobbi.

Other Information

Date Public:	2008-04-14
Date First Published:	2008-04-21
Date Last Updated:	2008-04-29
CERT Advisory:
CVE-ID(s):	CVE-2008-1100; CVE-2008-0314
NVD-ID(s):	CVE-2008-1100 CVE-2008-0314
US-CERT Technical Alerts:
Metric:	3.94
Document Revision:	31

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Produced 2008 by US-CERT, a government organization
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