ASA-2019-00653 – OpenBSD: Local privilege escalation via S/Key and YubiKey

OpenBSD, in a non-default configuration where S/Key or YubiKey authentication is enabled, allows local users to become root by leveraging membership in the auth group. This occurs because root's file can be written to /etc/skey or /var/db/yubikey, and need not be owned by root.

ASA-2019-00652 – OpenBSD: libc’s authentication layer performed insufficient username validation

libc in OpenBSD allows authentication bypass via the -schallenge username, as demonstrated by smtpd, ldapd, or radiusd. This is related to gen/auth_subr.c and gen/authenticate.c in libc (and login/login.c and xenocara/app/xenodm/greeter/verify.c).

ASA-2019-00650 – OpenBSD: Local privilege escalation via su

A local attacker can exploit su's -L option ("Loop until a correct username and password combination is entered") to log in as themselves but with another user's login class (with the exception of root's login class if the attacker is not in the group "wheel"), because the class variable is set once and never reset.