Cisco IOS 12.2 and 15.0 through 15.2 on Cisco 10000 series routers, when a tunnel interface exists, allows remote attackers to cause a denial of service (interface queue wedge) via tunneled (1) GRE/IP, (2) IPIP, or (3) IPv6 in IPv4 packets, aka Bug ID CSCts66808.
https://exchange.xforce.ibmcloud.com/vulnerabilities/78883
http://www.securitytracker.com/id?1027578
http://www.securityfocus.com/bid/55696
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-c10k-tunnels