A software developer has uncovered a bug in most versions of Linux that could allow untrusted users to gain complete control over the open-source operating system.

The null pointer dereference flaw was only fixed in the upcoming 2.6.32 release candidate of the Linux kernel, making virtually all production versions in use at the moment vulnerable. While attacks can be prevented by implementing a common feature known as mmap_min_addr, the RHEL distribution, short for Red Hat Enterprise Linux, doesn't properly implement that protection, Brad Spengler, who discovered the bug in mid October, told The Register.

What's more, many administrators are forced to disable the feature so their systems can run developer tools or desktop environments such as Wine.

The vulnerability was first reported by Spengler, a developer at grsecurity, a maker of applications that enhance the security of Linux. On October 22, he wrote a proof of concept attack for the local root exploit. Over the past few months, he has emerged as an outspoken critic of security practices followed by the team responsible for the Linux kernel.

Over the past few months, he has emerged as an outspoken critic of security practices followed by the team responsible for the Linux kernel.