In Sudo before 1.8.28, an attacker with access to a Runas ALL sudoer account can bypass certain policy blacklists and session PAM modules, and can cause incorrect logging, by invoking sudo with a crafted user ID. For example, this allows bypass of !root configuration, and USER= logging, for a "sudo -u \#$((0xffffffff))" command.

Affected: Ubuntu:Pro:14.04:LTS: sudo, Ubuntu:16.04:LTS: sudo, Ubuntu:18.04:LTS: sudo

Joe Vennix discovered that Sudo incorrectly handled certain user IDs. An attacker could potentially exploit this to execute arbitrary commands as the root user.