USN-4156-1 fixed several vulnerabilities in SDL. This update provides the corresponding update for Ubuntu 12.04 ESM and Ubuntu 14.04 ESM.
Original advisory details:
It was discovered that SDL incorrectly handled certain images. If a user were tricked into opening a crafted image file, a remote attacker could use this issue to cause SDL to crash, resulting in a denial of service, or possibly execute arbitary code.