Friday, March 23, 2007

"Etherleak" -- Old dog, old tricks

On 04/27/2002, I disclosed on the Linux Kernel Mailing list, a vulnerability that would be come known as the 'etherleak' bug. In various situations an ethernet frame must be padded to reach a specific size or fall on a certain boundary. This task is left up to the driver for the ethernet device. The RFCs state that this padding must consist of NULLs. The bug is that at the time and still to this day, many device drivers do not pad will NULLs, but rather pad with unsanitized portions of kernel memory, oftentimes exposing sensitive information to remote systems or those savvy enough to coerce their targets to do so.

Proof of this can be found by googling for "remote memory reading using arp", or by visiting the original posting. Admittedly, I did not realize at the time the exact cause of the bug nor the scope, but to my knowledge this was the first public disclosure.

This was ultimately fixed in the Linux kernel, but over time this vulnerability reared its head numerous times, but at the core the vulnerability was the same as the one I originally published. The most public of these was CVE-2003-0001, which was assigned to address an official @stake advisory which did not credit my findings.

So, now, nearly 5 years later, I'm publishing the POC exploit code I've recently revamped that can demonstrate the issue. The good news is that the bug has been addressed by numerous vendors, but is still rampant and should be considered a threat.

Enjoy.

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