Symantec is warning Mac OS X users that the addition of an exploit to the Metasploit hacking framework had boosted the threat posed by an unpatched bug in Samba, the open-source file- and print-sharing software included with the Apple operating system.

Although the vulnerability was disclosed 14 May and patched that same day by the Samba community, Apple has not updated Mac OS X with a fix, said Symantec's Alfred Huger, vice president of engineering with the security company's response group.

"This is significant exposure for Mac OS X users," said Huger. "Samba is used in virtually every mixed environment where there are Macs and PCs, and the threat profile is much higher now that an exploit has been added to Metasploit."

Samba, which is also used by most Linux distributions to file- and print-sharing with Windows systems, is turned on in Mac OS X when users activate the Windows Sharing feature.

This month, a trio of Brazilian researchers who collaborate as Rise Security released Mac OS X attack code for the Samba vulnerability. According to Symantec, the Rise code is "almost identical" to what the company's security team discovered in late May.

More important, said Huger, is that Rise also contributed their code to Metasploit, an open-source platform for creating, testing and launching exploit code. "Once we see something in Metasploit, we know it's likely we'll see it used in attacks," he said as he explained why Symantec had amped its earlier warning. "Every Unix-based break-in that's not hand-crafted, in other words not with the attacker sitting at the keyboard during the attack, is made with a couple of different tools, and Metasploit is by far the most popular."

The Rise-developed, Metasploit-distributed exploit successfully attacks a fully-patched Mac OS X 10.4.10 system, added Symantec, and results in the attacker gaining root privileges on the Mac.

"There is a very high probability that attackers will attempt to leverage [the exploit] to compromise Apple users, especially those connected to wireless networks," said Symantec in a separate alert issued Wednesday to customers of its DeepSight Threat network. "Wireless networks are an especially high threat, because users' systems may be exposing the service that may otherwise be protected by a gateway firewall installed on a home network."

Symantec recommended that users disable the Windows Sharing service until Apple produces a patch. Technically-astute users, however, may be able to handle the more rigorous chore of compiling the latest version of Samba manually in lieu of waiting for Apple.

Apple has not updated Samba within Mac OS X since March 2005.