Ubuntu Security Notice 959-1 – Denis Excoffier discovered that the PAM MOTD module in Ubuntu did not correctly handle path permissions when creating user file stamps. A local attacker could exploit this to gain root privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/91595/USN-959-1.txt
Source: https://packetstormsecurity.com/files/91595/Ubuntu-Security-Notice-959-1.html