The ALG module in Cisco IOS 15.0 through 15.4 does not properly implement SIP over NAT, which allows remote attackers to cause a denial of service (device reload) via multipart SDP IPv4 traffic, aka Bug ID CSCun54071.
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140924-nat
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140924-nat/cvrf/cisco-sa-20140924-nat_cvrf.xml
www.securityfocus.com/bid/70129
www.securitytracker.com/id/1030896
exchange.xforce.ibmcloud.com/vulnerabilities/96181