Description
OpenBSD 6.6, 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.
References
- https://www.openwall.com/lists/oss-security/2019/12/04/5
- https://www.openbsd.org/errata66.html
- [oss-security] 20191204 Authentication vulnerabilities in OpenBSD mailing-list
- 20191205 Authentication vulnerabilities in OpenBSD mailing-list
- http://packetstormsecurity.com/files/155572/Qualys-Security-Advisory-OpenBSD-Authentication-Bypass-Privilege-Escalation.html
- 20191206 Authentication vulnerabilities in OpenBSD mailing-list