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://bugs.debian.org/cgi-bin/bugreport.cgi?bug=711600
http://seclists.org/oss-sec/2013/q2/528
http://secunia.com/advisories/54300
http://ubuntu.com/usn/usn-1909-1