Race condition in the post-installation script (mysql-server-5.5.postinst) for MySQL Server 5.5 for Debian GNU/Linux and Ubuntu Linux creates a configuration file with world-readable permissions before restricting the permissions, which allows local users to read the file and obtain sensitive information such as credentials.
http://www.securityfocus.com/bid/60424
http://www.debian.org/security/2013/dsa-2818
http://ubuntu.com/usn/usn-1909-1