- Testers recently found a vulnerability in the Session Initiation Protocol (SIP), an emerging standard used for connections between devices in IP networks such as voice-over-IP phones. But several vendors and analysts say they have heard no reports of significant problems from users.
The CERT Coordination Center at Carnegie Mellon University in Pittsburgh reported the vulnerability last week, citing a discovery by the Oulu University Secure Programming Group (OUSPG) in Finland (see SIP weakness could expose VoIP gear to attacks). The OUSPG found that when a certain SIP test is applied to SIP clients and proxy servers, it causes unexpected system behavior or a denial of service.
A Cisco Systems spokesman says the company has heard no complaints from its customers. But Cisco posted an advisory February 21 saying the vulnerability affects two Cisco IP phones, the 7940 and 7960, among several other products. Some recommendations call for work-arounds or patches, depending on the device affected.
CERT says Nortel Networks is working on a software patch to address the vulnerability in its Succession Communications servers. That patch is due out by the end of the month.
John Pescatore, an analyst at Gartner in Stamford, Connecticut, says it is significant that the vulnerability doesn't affect two major instant messaging protocols from Microsoft and America Online and that it seems to apply mainly to telephone clients. CERT has listed more than 80 vendors that make SIP-dependent products along with whether those products are affected. The group was still making updates to the list today.
David Fraley, also an analyst at Gartner, predicted in December that SIP would prove to have vulnerabilities that could invite security breaches. When he learned of the CERT warning this week, he says the vulnerability test is a welcome event that will help make SIP more rigorous.
"SIP is a very young protocol, and the way to get it mature is to have this kind of rigorous testing to occur," Fraley says. "I would much rather Oulu find this than some hacker group."
He urges companies and other users to take the time to research whether their products are vulnerable and to apply the needed patches or work-arounds.