strongswan vulnerability

USN-5250-1 fixed a vulnerability in strongSwan. This update provides
the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

Original advisory details:

Zhuowei Zhang discovered that stringSwan incorrectly handled EAP
authentication. A remote attacker could use this issue to cause strongSwan
to crash, resulting in a denial of service, or possibly bypass client and
server authentication.