A vulnerability in the popular open-source ClamAV anti-virus scanner can be exploited by attackers to execute malicious code.
The warning on 14 April from a security company pompted a swift response from the ClamAV team, which updated the scanner to fix the flaw.
According to Danish bug-tracking company Secunia , a vulnerability within the ""cli_scanpe()" function in "libclamav/pe.c" could be exploited with a rigged "Upack" file.
In a warning posted Monday Secunia credited one of its own researchers, Alin Rad Pop, with finding and reporting the bug, and ranked the threat as "highly critical," its second-highest rating.
ClamAV is most often used to scan incoming files attachments at an email gateway; although it's designed for UNIX, versions are available for Windows. Apple also packages ClamAV with its server operating systems, including the current production version of Mac OS X Server 10.5.
About a month ago, Apple issued a massive security update that fixed nearly 90 vulnerabilities in its operating systems, including nine ClamAV bugs present in Server 10.5, to bring Mac OS X's version in line with the still current ClamAV 0.90.3.
ClamAV version 0.93 patches the vulnerability disclosed today, and can be downloaded from the open-source project's website.
Prior to issuing the patch, ClamAV had remotely disabled the vulnerable module, said a ClamAV spokesman. "Note that 1 week ago the vulnerable module has been switched off via DCONF using a special CVD update so older installations cannot be exploited," said Luca Gibelli in an email.
Users unable to deploy the patch who have also not updated ClamAV's signatures - the program received those as CVD, or ClamAV Virus Database file - should not scan untrusted PE (Portable Executable) files, Secunia recommended.