Ubuntu Security Notice USN-670-1 -Mathias Gug discovered that vm-builder improperly set the root password when creating virtual machines. An attacker could exploit this to gain root privileges to the virtual machine by using a predictable password.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/71959/USN-670-1.txt
Source: https://packetstormsecurity.com/files/71959/Ubuntu-Security-Notice-670-1.html