Ivan Gotovchits discovered that ppp incorrectly handled the EAP-TLS
protocol. A remote attacker could use this issue to cause ppp to crash,
resulting in a denial of service, or possibly bypass authentication.
The problem can be corrected by updating your system to the following
Ubuntu 18.04 LTS:
Ubuntu 16.04 LTS:
Ubuntu 14.04 LTS:
In general, a standard system update will make all the necessary changes.