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.

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 allows local users to specify an alternate proxy using the krb4_proxy variable, which allows the user to generate false proxy responses and possibly gain privileges.

KTH Kerberos IV allows local users to change the configuration of a Kerberos server running at an elevated privilege by specifying an alternate directory using with the KRBCONFDIR environmental variable, which allows the user to gain additional privileges.

Buffer overflow in the kdc_reply_cipher function in KTH Kerberos IV allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long authentication request.

KTH Kerberos IV allows local users to overwrite arbitrary files via a symlink attack on a ticket file.

Kerberos 4 allows remote attackers to obtain sensitive information via a malformed UDP packet that generates an error string that inadvertently includes the realm name and the last user.