USN-5355-1 fixed a vulnerability in zlib. This update provides the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.
Original advisory details:
Danilo Ramos discovered that zlib incorrectly handled memory when performing certain deflating operations. An attacker could use this issue to cause zlib to crash, resulting in a denial of service, or possibly execute arbitrary code.
1:1.2.8.dfsg-1ubuntu1.1+esm11:1.2.8.dfsg-2ubuntu4.3+esm1