A major flaw that imperils Linux users of Wi-Fi has been found in the widely-used MadWiFi Linux kernel device driver for Atheros-based Wi-Fi chipsets.

The kernel stack-overflow bug could be used to take control of computers, even if they are not on a Wi-Fi network.

"You may be vulnerable if you do not manually patch your MadWi-Fi driver," Laurent Butti, a researcher from France Telecom Orange who discovered the issue, told the Washington Post.

Butti gave details of the flaw at last month's Black Hat Briefing convention, where security researchers and hackers meet to exchange ideas and information.

But the news was held back from general release until a patch had been built and distributed.

Butti found the flaw by 'fuzzing' the code. This involves feeding the software random data until it crashes and reveals a flaw.

He is now turning his attention to WiMax and wireless USB.