Cisco IOS 12.0 through 12.4 allows remote attackers to cause a denial of service via (1) a malformed MGCP packet, which causes a device hang, aka CSCsf08998; a malformed H.323 packet, which causes a device crash, as identified by (2) CSCsi60004 with Proxy Unregistration and (3) CSCsg70474; and a malformed Real-time Transport Protocol (RTP) packet, which causes a device crash, as identified by (4) CSCse68138, related to VOIP RTP Lib, and (5) CSCse05642, related to I/O memory corruption.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5570
https://exchange.xforce.ibmcloud.com/vulnerabilities/35905
https://exchange.xforce.ibmcloud.com/vulnerabilities/35904
https://exchange.xforce.ibmcloud.com/vulnerabilities/35903
http://www.vupen.com/english/advisories/2007/2816
http://www.securityfocus.com/bid/25239
http://www.cisco.com/en/US/products/products_security_advisory09186a0080899653.shtml
http://securitytracker.com/id?1018533