Cybersecurity researchers have shed light on a new Linux kernel exploitation technique called SLUBStik which can be used to increase the vulnerability of a bounded heap to arbitrary memory read and write primitives.
“Firstly, it uses the side channel of the allocator time to perform a cross-cache attack reliably,” a group of scientists from the Graz University of Technology. said (PDF). “When specific, using side-channel leaks increases the success rate to 99% for commonly used shared caches.”
Memory security vulnerabilities affecting the Linux kernel have limited capabilities and are much more difficult to exploit due to security features such as supervisor-mode access prevention (SMAP), randomization of kernel address space location (KASLR), and kernel control flow integrity (kCFI).
While cross-cache software attacks were developed as a way to counter kernel-hardening strategies such as coarse-grained heap partitioning, research has shown that existing methods have only a 40% success rate.
SLUBStick was demonstrated in Linux kernel versions 5.19 and 6.2 using nine security flaws (such as double-free, use-after-free, and out-of-write) discovered between 2021 and 2023, which resulted in the elevation of root privileges from no authentication and exit containers.
The main idea behind this approach is to offer the ability to modify kernel data and obtain an arbitrary primitive for reading and writing memory in a way that reliably defeats existing defenses such as KASLR.
However, for this to work, the threat model assumes that there is a heap vulnerability in the Linux kernel and that an unprivileged user has code execution capabilities.
“SLUBStick exploits newer systems, including v5.19 and v6.2, for a wide range of heap vulnerabilities,” the researchers said.
