pam_krb5 2.2.14 through 2.3.4, as used in Red Hat Enterprise Linux (RHEL) 5, generates different password prompts depending on whether the user account exists, which allows remote attackers to enumerate valid usernames.

Russ Allbery pam-krb5 before 3.13, when linked against MIT Kerberos, does not properly initialize the Kerberos libraries for setuid use, which allows local users to gain privileges by pointing an environment variable to a modified Kerberos configuration file, and then launching a PAM-based setuid application.