Here is a way to reset or hack superuser password, provided you have physical access to reboot the system and username. All you need to do is just reboot the system and then follow these instructions.

Security researcher Dan Rosenberg presents a small demo program which combines several security holes to obtain root privileges on Linux systems on Full Disclosure Security mailing list.

He combined some existing vulnerabilities with the vulnerability discovered by Nelson Elhage in connection with the kernel’s thread management and troubleshooting routines (CVE-2010-4258).With this exploit, an attacker can potentially exploit an OOPS to write a null byte into the kernel’s memory area.