Cisco Security Advisory – Multiple vulnerabilities exist in the Session Initiation Protocol (SIP) implementation in Cisco IOS Software that could allow an unauthenticated, remote attacker to cause a reload of an affected device when SIP operation is enabled. Remote code execution may also be possible. Cisco has released free software updates that address these vulnerabilities. For devices that must run SIP there are no workarounds; however, mitigations are available to limit exposure of the vulnerabilities.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/87601/cisco-sa-20100324-sip.txt
Source: https://packetstormsecurity.com/files/87601/Cisco-Security-Advisory-20100324-sip.html