USN-3968-1 fixed a vulnerability in Sudo. This update provides the corresponding update for Ubuntu 14.04 ESM.
Original advisory details:
It was discovered that Sudo did not properly parse the contents of /proc/[pid]/stat when attempting to determine its controlling tty. A local attacker in some configurations could possibly use this to overwrite any file on the filesystem, bypassing intended permissions. (CVE-2017-1000368)