Ubuntu Security Notice USN-74-1 – Jean-Samuel Reynaud noticed a programming error in the IPv6 handling code of Postfix when /proc/net/if_inet6 is not available (which is the case in Ubuntu since Postfix runs in a chroot).
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/36031/USN-74-1.txt
Source: https://packetstormsecurity.com/files/36031/Ubuntu-Security-Notice-74-1.html