The Session Initiation Protocol (SIP) implementation in Nortel Networks Succession Communication Server 2000, when using SIP-T, allows remote attackers to cause a denial of service and possibly execute arbitrary code via crafted INVITE messages, as demonstrated by the OUSPG PROTOS c07-sip test suite.
https://exchange.xforce.ibmcloud.com/vulnerabilities/11379
http://www.securityfocus.com/bid/6904