FreeBSD Security Advisory FreeBSD-SA-05:03 – The AMD64 architecture has two mechanisms for permitting processes to access hardware: Kernel code can access hardware directly by reason of its elevated privilege level, while user code can access a subset of hardware determined by a bitmap. The bitmap which determines which hardware can be accessed by unprivileged processes was not initialized properly. Unprivileged users on amd64 systems can gain direct access to some hardware, allowing for denial of service, disclosure of sensitive information, or possible privilege escalation.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/37023/FreeBSD-SA-05-03.amd64.txt
Source: https://packetstormsecurity.com/files/37023/FreeBSD-SA-05-03.amd64.txt.html