Security researchers have warned that Snort, a popular intrusion-detection and prevention sensor, could leave networks open to attack.
The flaw is found in a Snort component used to handle packets from the Back Orifice hacking tool. It could allow an attacker to take complete control of a Snort sensor, granting root privileges and allowing for further system compromise, according to Internet Security Systems (ISS), which originally discovered the flaw.
Snort is widely used, and is also the basis for many commercial IDS and IPS products, which are also likely to be affected, ISS said. The bug can be triggered with a single UDP packet targeting nearly any port, which could make it easier to get around perimeter firewalls.
An attacker doesn't need to target a particular Snort installation, but just to aim at a network that may be monitored by Snort, ISS said. These factors mean the bug is likely to be exploited by a worm, the company said.
"Due to the trivial nature of this vulnerability and its potential to bypass perimeter firewalls, there is grave concern that this issue might be exploited as part of a network-based worm," said ISS in its advisory.
ISS passed its research on to Sourcefire -- Snort's parent company -- via US-CERT last week, according to Sourcefire. ISS, US-CERT and Sourcefire all published advisories on the flaw on Tuesday, along with a patched version of Snort and instructions for reducing the danger from the flaw.
Administrators may be able to head off the problem by disabling the Back Orifice preprocessor, researchers said; instructions are contained in ISS' and Sourcefire's advisories.
Sourcefire disagreed with ISS over the severity of the flaw, saying it would be difficult for attackers to fully exploit the bug across different builds of Snort on different platforms or even different compiler versions on a single platform. "It is more likely that an attacker could use the vulnerability as a denial of service attack," Sourcefire stated.
The bug affects all Snort versions since 2.4.0, and has been fixed in the new version 2.4.3, Sourcefire and ISS said.
Check Point Software is currently in the process of buying Sourcefire for US$225 million.