This question is brought up every time this happens. Ubuntu uses stable (old) versions and does not upgrade to latest (unstable) releases very often. However, they do back port and apply security patches to these old versions.
Point in case: 16.04 TLS is still on 2.7.4 but it is fully patched and secure.
Point in case: 16.04 TLS is still on 2.7.4 but it is fully patched and secure.