A developer who helped write the original Linux kernel is warning of a flaw in some versions of the operating system that could allow a malicious local user to gain root control of a Linux computer.

Linux expert Alan Cox, who worked with Linus Torvalds on building the open source operating system's original kernel, posted the warning about the 'ptrace' debugging tool on a Linux developers' mailing list here.

Cox explained that the vulnerability could not be exploited remotely. "The Linux 2.2 and 2.4 kernels have a flaw in ptrace," he said.

"This hole allows local users to obtain full privileges. Remote exploitation of this hole is not possible. Linux 2.5 is not believed to be vulnerable.

"Linux 2.2.25 has been released to correct Linux 2.2. It contains no other changes.

"The bug fixes that would have been in 2.2.5pre1 will now appear in 2.2.26pre1. The patch will apply directly to most older 2.2 releases."

Linux company Red Hat has posted a patch for Red Hat 7.1, 7.2, 7.3, and 8.0 here.

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