The LAN-to-LAN IPSEC capability for Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.4, allows remote attackers to cause a denial of service via an incoming LAN-to-LAN connection with an existing security association with another device on the remote network, which causes the concentrator to remove the previous connection.
https://exchange.xforce.ibmcloud.com/vulnerabilities/10027
http://www.securityfocus.com/bid/5622
http://www.cisco.com/warp/public/707/vpn3k-multiple-vuln-pub.shtml