Mac OS X 10.4.6 Update
03 Apr 2006

Firmware
CVE-ID: CVE-2006-0401

Available for: Mac OS X v10.4.5, Mac OS X Server v10.4.5

Impact: Firmware password can be bypassed on Intel-based Macintosh computers

Description: Intel-based Macintosh computers support the firmware password feature. Prior to this update, a person with physical access to the computer could bypass the firmware password and access Single User Mode. This update addresses the issue by enhancing the security provided by the firmware password. Credit to David Pugh of the University of Michigan for reporting this issue.

http://docs.info.apple.com/article.html?artnum=61798