Multiple memory leaks in Cisco IOS 15.1 before 15.1(4)M7 allow remote attackers to cause a denial of service (memory consumption or device reload) by sending a crafted SIP message over (1) IPv4 or (2) IPv6, aka Bug IDs CSCuc42558 and CSCug25383.
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20131106-sip