MIT Kerberos 4

Version 4 of the Kerberos protocol (krb4), as used in Heimdal and other packages, allows an attacker to impersonate any principal in a realm via a chosen-plaintext attack.

Certain weaknesses in the implementation of version 4 of the Kerberos protocol (krb4) in the krb5 distribution, when triple-DES keys are used to key krb4 services, allow an attacker to create krb4 tickets for unauthorized principals using a cut-and-paste attack and "ticket splicing."

Kerberos 4 (aka krb4) allows local users to overwrite arbitrary files via a symlink attack on new ticket files.