USN-5359-1 fixed vulnerabilities in rsync. This update provides the corresponding updates for Ubuntu 16.04 ESM.
Original advisory details:
Danilo Ramos discovered that rsync incorrectly handled memory when performing certain zlib deflating operations. An attacker could use this issue to cause rsync to crash, resulting in a denial of service, or possibly execute arbitrary code.
3.1.1-3ubuntu1.3+esm1