The Clamav development team released version 0.90 of their open-source antivirus toolkit today. This version contains fixes for security vulnerabilities described in a number of iDefense advisories that were published today.

ClamAV CAB File Denial of Service Vulnerability (CVE-2007-0898)
Remote attackers can perform a service degradation attack by sending a malformed CAB file through a gateway scanner running ClamAV. The vulnerability can prevent ClamAV from scanning archives succesfully by depleting the available local file descriptors. iDefense investigated a number of common setups and observed that in most cases, mails that cannot be scanned will be auto-denied.

ClamAV MIME Parsing Directory Traversal Vulnerability (CVE-2007-0897)
An input validation bug allows a remote user to overwrite files on the system that are owned by the clamd scanner. A potential target mentioned in the advisory is the virus database. By overwriting this file, the scanner's effectiveness against certain threats can be reduced significantly.

Both vulnerabilities were resolved in ClamAV's new stable 0.90 release, which was released yesterday. Do note that users that automatically download and install signature updates are not automatically covered. When vulnerabilities in anti virus software are addressed, it is important to understand whether they are fixed in the signatures or scanning engines.

Depending on the solution in use, most setups are configured to automatically update the former, while the latter may require separate upgrades. One user wrote in with the really good idea of leveraging the common logwatch tool to check for the typical Freshclam error:

WARNING: Your ClamAV installation is OUTDATED!
WARNING: Local version: 0.88.7 Recommended version: 0.90