As you may know, Canonical keeps upgrading its Ubuntu systems on a regular basis, while working at the new projects.
Today, Canonical has upgraded Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr and Ubuntu 12.04 Precise Pangolin, fixing a kernel vulnerability on all their supported systems.
So, in order to stay safe, just perform a system upgrade on your Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr, Ubuntu 12.04 Precise Pangolin or a derivative system like Linux Mint 17.2 Rafaela, Linux Mint 17.1 Rebecca, Linux Mint 17 Qiana, Linux Mint 13 Maya, Pinguy OS 14.04, Elementary OS 0.3 Freya, Deepin 2014, Peppermint 6, Peppermint 5, LXLE 14.04 and Linux Lite 2. Like this:
$ sudo apt-get update
$ sudo apt-get dist-upgrade
Depending on your system, Ubuntu 15.04 or the derivative will use Kernel 3.19.0-26.28, Ubuntu 14.04 or the derivative Kernel 3.13.0-62.102 and Ubuntu 12.04 or the derivative Kernel 3.2.0-89.127, unless you are using other kernel versions instead of the stock ones.