Ubuntu Security Notice USN-226-1 – Patrick Cheong Shu Yang discovered a flaw in the user account handling of courier-authdaemon. After successful authorization, the Courier mail server granted access to deactivated accounts.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/42259/USN-226-1.txt
Source: https://packetstormsecurity.com/files/42259/Ubuntu-Security-Notice-226-1.html