Cisco VPN 3000 series concentrators and Cisco VPN 3002 Hardware Client 2.x.x through 3.6.7A allow remote attackers to cause a denial of service (slowdown and possibly reload) via a flood of malformed ICMP packets.
https://exchange.xforce.ibmcloud.com/vulnerabilities/11956
http://www.kb.cert.org/vuls/id/221164
http://www.cisco.com/warp/public/707/cisco-sa-20030507-vpn3k.shtml