KTH Kth Kerberos 5

The Kerberos Telnet protocol, as implemented by KTH Kerberos IV and Kerberos V (Heimdal), does not encrypt authentication and encryption options sent from the server, which allows remote attackers to downgrade authentication and encryption mechanisms via a man-in-the-middle attack.

KTH Kerberos IV and Kerberos V (Heimdal) for Telnet clients do not encrypt connections if the server does not support the requested encryption, which allows remote attackers to read communications via a man-in-the-middle attack.