Ubuntu Security Notice USN-182-1 – A local privilege escalation vulnerability has been discovered in the pixmap allocation handling of the X server. By allocating a huge pixmap, a local user could trigger an integer overflow that resulted in a memory allocation that was too small for the requested pixmap. This resulted in a buffer overflow which could eventually be exploited to execute arbitrary code with full root privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/39993/USN-182-1.txt
Source: https://packetstormsecurity.com/files/39993/Ubuntu-Security-Notice-182-1.html