Ubuntu Security Notice USN-702-1 – Gunter Hockel discovered that Samba with registry shares enabled did not properly validate share names. An authenticated user could gain access to the root filesystem by using an older version of smbclient and specifying an empty string as a share name. This is only an issue if registry shares are enabled on the server by setting “registry shares = yes”, “include = registry”, or “config backend = registry”, which is not the default.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/73608/USN-702-1.txt
Source: https://packetstormsecurity.com/files/73608/Ubuntu-Security-Notice-702-1.html