Multimedia vulns pose severe risk
This could get messy
Numerous VoIP and video conferencing products are subject to serious security vulnerabilities because of widespread flaws in the implementation of a key multimedia protocol, according to an advisory by security clearing house CERT published yesterday.
The issue revolves around faulty implementations of H.323, the multimedia telephony protocol, affecting a wide variety of networking kit including VoIP and video conferencing gear, media gateways and Session Initiation Protocol (SIP) devices and software. The products of numerous vendors, including Cisco , Microsoft  and Nortel, are affected. H.323 is an international standard protocol used to facilitate communication among telephony and multimedia systems.
The flaws came to light as a result of testing by the U.K. National Infrastructure Security Co-ordination Centre (NISCC), which has produced an advisory .
Exploitation of the vulnerabilities could be used to crash networking devices or run malicious code, CERT warns.
CERT's advisory  contains a fuller list of vendors whose technologies may be affected by the vulnerabilities. Vendors are in the process of releasing patches, which users are urged to review as quickly as possible. As a workaround, sys admins are advised to apply filters to block access to the H.323 services at the network gateway.
This process is complicated because firewalls process H.323 packets and could themselves be vulnerable to attack. For this reason, users might want to disable application layer inspection of H.323 network packets until fixes are available.
CERT warns "protecting your infrastructure against these vulnerabilities may require careful coordination among application, computer, network, and telephony administrators. You may have to make trade-offs between security and functionality until vulnerable products can be updated." ®