StackRot – New Linux kernel Privilege Escalation Vulnerability

A security flaw has been identified in the Linux kernel called “stockRot” (CVE-2023-3269). This vulnerability grants attackers access to the kernel and the ability to elevate their privileges.

It has been discovered that “Stack Rot,” a vulnerability in stack expansion, is present in Linux kernel versions 6.1 to 6.4.

The stack is a section of memory that operates on a LIFO (last-in-first-out) principle, which means that data such as your local variables and function calls are appended to or removed from the stack in reverse chronological order.

Vulnerability in Memory Management

There is a vulnerability in the memory management subsystem of the Linux kernel that can impact almost all kernel configurations. It can be triggered with minimal capabilities.

The maple tree, responsible for managing virtual memory areas, can undergo node replacement without properly acquiring the MM write lock, leading to use-after-free issues.

The Maple Tree is a B-Tree data type that is optimized for storing non-overlapping ranges; the maple tree is composed of maple nodes.

The StackRot vulnerability has been present in the Linux kernel since version 6.1 when the VMA tree structure was changed from red-black trees to maple trees.

“However, it should be noted that maple nodes are freed using RCU callbacks, delaying the actual memory deallocation until after the RCU grace period. Consequently, exploiting this vulnerability is considered challenging”, the researcher said.

Peking University security researcher Ruihan Li said no publicly available exploits target use-after-free-by-RCU (UAFBR) bugs.

He also added that this flaw could be exploited in the environment provided by Google kCTF VRP.

Patch Released

The flaw was fixed during the merge window for Linux kernel 6.5; the fix was merged into Linus’ tree.

The patches applied to o stable kernels (6.1.37, 6.3.11, and 6.4.1), effectively resolving the “Stack Rot” bug on July 1st.

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