Ubuntu Security Notice 511-1 – It was discovered that the libraries handling RPCSEC_GSS did not correctly validate the size of certain packet structures. An unauthenticated remote user could send a specially crafted request and execute arbitrary code with root privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/59079/USN-511-1.txt
Source: https://packetstormsecurity.com/files/59079/Ubuntu-Security-Notice-511-1.html