Symantec's line of anti-virus software is vulnerable to attack, a prominent security researcher revealed Tuesday. The bug is currently unpatched, although Symantec has issued an advisory.

The vulnerability, which was discovered and reported by Alex Wheeler, is in how Symantec's AntiVirus Library, part of all the Cupertino, Calif.-based security giant's anti-virus products, handles RAR compressed files. RAR files are created by the WinRAR compression utility, developed and sold by RarLab.

The bug, labeled as "Highly critical" by Danish vulnerability tracker Secunia and "High" by Symantec itself, can cause a heap overflow, which then may let an attacker execute additional code. Bottom-line: the bug could result in a completely compromised machine.

"The issues can be leveraged remotely to gain complete control over the affected system," Symantec wrote in an alert Tuesday morning to customers of its DeepSight Threat Management System.

All editions of Symantec's Norton Internet Security and Norton AntiVirus, including AntiVirus for the Macintosh, are at risk, as are other products which include the Library. Those include such enterprise-specific lines as AntiVirus Corporate Edition, Brightmail Anti-Spam, Client Security, and Gateway Security.

Symantec has not issued a patch for the vulnerability, but the DeepSight alert recommended that users disable scanning for RAR archive files.

Wheeler is well known among researchers for his probing of security software weaknesses. Earlier in 2005, he disclosed a slew of vulnerabilities in software from major vendors like McAfee, Kaspersky Labs, F-Secure, and Trend Micro. All the bugs he has discovered involve how the various anti-virus scanning engines handle compressed files.

This is the second scanning vulnerability Wheeler has uncovered in Symantec's product line. In February, while working with Internet Security Systems, a Symantec rival, he announced a bug in how Symantec's scanning engine could be hacked as it sniffed through UPX-formatted files.