Linux Privilege Escalation Hole Detected

For the second time in as many months, security researchers have
uncovered a privilege escalation security flaw in the Linux kernel.

According to an advisory from computer security consultants iSEC Security Research, the flaw was found in the Linux kernel memory management code and is completely unrelated to a similar vulnerability reported in February.

The flaw carries a “critical” rating and affects Linux versions 2.2 up to and including 2.2.25; it also impacts versions 2.4 up to and including 2.4.24 as well as versions 2.6 up to and including 2.6.2.

“Proper exploitation of this vulnerability leads to local privilege escalation giving an attacker full super-user privileges. The vulnerability may also lead to a denial-of-service attack on the available system memory,” iSEC warned.

Linux distributor Gentoo confirmed its implementation of the open source operating system was susceptible to the flaw and strongly urged uses to upgrade to newer, more secure versions.

According to Gentoo, arbitrary code with normal non-superuser privileges may be able to exploit this vulnerability and may disrupt the operation of other parts of the kernel memory management subroutines.

Proper exploitation of this vulnerability may lead to local privilege escalation allowing for the execution of arbitrary code with kernel level root access,” Gentoo warning, noting that proof-of-concept exploit code has been created and successfully tested.

The flaw was discovered in the memory subsystem which allows for
shrinking, growing, and moving of chunks of memory along any of the
allocated memory areas which the kernel possesses. iSEC Security Research found that the code doesn’t check the return value of the memory function.

“Due to the missing return value check after trying to unmap the middle of the first memory area, the corresponding page table entries from the second new area are inserted into the page table locations described by the first old one, thus they are subject to page protection flags of the first area. As a result, arbitrary code can be executed,” the company explained.

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