Cisco IOS 12.1(2)T, 12.1(3)T allow remote attackers to cause a denial of service (reload) via a connection to TCP ports 3100-3999, 5100-5999, 7100-7999 and 10100-10999.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6589
http://www.securityfocus.com/bid/2804
http://www.cisco.com/warp/public/707/ios-tcp-scanner-reload-pub.shtml