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.
CWE-287 - Improper Authentication
Improper (or broken) authentication attacks are widespread, and have accounted for many of the worst data breaches in recent years. Improper authentication attacks are a class of vulnerabilities where an attacker impersonates a legitimate user by exploiting weaknesses in either session management or credential management to gain access to the user’s account. This can result in disclosure of sensitive information, and can lead to system compromise, theft, identity theft, and fraud.