The remote host is running a version of Cisco IOS that is being targeted by a Denial of Service attack vector.
Versions of Cisco a flaw that is triggered when handling Cluster Management Protocol-specific Telnet options while establishing a Telnet session on a device which accepts Telnet connections. This may allow a remote attacker to potentially execute arbitrary code or cause a DoS.
Disabling the Telnet protocol as an allowed protocol for incoming connections would eliminate the exploit vector. Disabling Telnet and using SSH is recommended by Cisco.