Ubuntu Security Notice 280-1 – The Render extension of the X.org server incorrectly calculated the size of a memory buffer, which led to a buffer overflow. A local attacker could exploit this to crash the X server or even execute arbitrary code with root privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/46108/USN-280-1.txt
Source: https://packetstormsecurity.com/files/46108/Ubuntu-Security-Notice-280-1.html