The vulnerability affects McAfee's Antivirus Library, a collection of common code shared among the security software company's various virus scanners, including GroupShield for mail servers and VirusScan for PCs. An attacker could use the flaw to cause a vulnerable system to run a file instead of scanning it for malicious code.
While the company just learned of the issue recently, an update offered to corporate customers in November and consumers in December added security measures that fixed the problem.
"Once the update was released, all current subscribers got the fix," said Marc Solomon, senior product manager for McAfee. "For anyone who is no longer a subscriber, this is a reminder to renew."
The flaw is the fourth antivirus security vulnerability found by Internet Security Systems, which sells software and hardware to protect networks and corporate PCs. The company also has found flaws in the antivirus libraries developed by security software companies, and . Another flaw in Computer Associates International's antivirus software was .
Internet Security Systems would not specify how the problems were found, but a representative stressed that the company didn't target the products.
Users of McAfee's virus scanning software, also known as an engine, are vulnerable only if the software has not been updated through a current subscription and the person has not downloaded the latest virus definitions file, or DAT, from the company.
The flaw could be exploited using any type of network traffic that is scanned by a McAfee product, including e-mail, Web browsing and Windows file sharing. When the vulnerable software attempted to open a malicious file, the software would instead run the program included in the file.
The flaw occurs in how McAfee's software, based on the older library, scans files that are compressed using a format known as LHA. A specially crafted file, when scanned by vulnerable McAfee software, can execute its program.