USN-3410-1 fixed a vulnerability in GD Graphics Library.
This update provides the corresponding update for Ubuntu 12.04 ESM.
Original advisory details:
It was discovered that the GD Graphics Library (aka libgd) incorrectly handled
certain malformed PNG images. A remote attacker could use this issue to cause
the GD Graphics Library to crash, resulting in a denial of service, or possibly
execute arbitrary code.