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FreeBSD bug gives untrusted root access

'Unbelievably simple' exploit

A security bug in the latest version of FreeBSD can be exploited to grant unprivileged users complete control over the operating system, a German researcher said Monday.

The flaw is present in FreeBSD 8.0 and is known to affect versions 7.1 and 7.2 of the open-source OS, Nikolaos Rangos told The Register. He said it was "unbelievably simple" to exploit. Shortly after he disclosed the flaw on the Full Disclosure mailing list, other researchers said they were able to confirm the bug.

FreeBSD Security Officer Colin Percival said the Full Disclosure post was the first his team had heard of the reported vulnerability. The team is currently investigating.

The bug resides in FreeBSD's run-time link editor. A binary run by an unprivileged user can be executed with administrative privileges in a restricted environment, Rangos said. That allows the user to obtain root access to the system. All that's required to run the exploit code, which Rangos included in his post, is a command shell.

To exploit the bug, hackers would need local access to the vulnerable machine. To use the attack code remotely, it's conceivable it could be used in concert with another vulnerability, such as one residing in a web application running on the box.

Rangos speculated a fix would be coming shortly.

"The bug is in the most recent versions of FreeBSD and normally local root vulnerabilities are quickly patched by the FreeBSD maintainers," he said. ®

Update

FreeBSD's Percival has issued an advisory here. It includes a patch that he says may or may not be final. He writes: "It is even possible (although highly doubtful) that this patch does not fully fix the issue or introduces new issues -- in short, use at your own risk (even more than usual)."

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