CVE-2001-1444 in Kerberos
Summary
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.
If you want to get best quality of vulnerability data, you may have to visit VulDB.