There is a serious remotely exploitable vulnerability in the Samba open-source software that could enable an attacker to gain root privileges without any authentication. The bug is in all versions of Samba from 3.0.0 to 3.3, but has been fixed in Samba 3.6.4, which is the current stable release. Samba is designed to help integrate Unix, Linux and other non-Windows clients into Windows environments. An attacker who found a vulnerable installation would not need to authenticate in order to launch an exploit.
Source: https://threatpost.com/remote-pre-authentication-flaw-fixed-samba-041112/76432/