CVE-2026-52927 netfilter: ebtables: fix OOB read in compat_mtw_from_user
A local attacker can trigger an out-of-bounds read in the Linux kernel's ebtables module, potentially disclosing sensitive kernel memory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52927?
CVE-2026-52927 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ebtables: fix OOB read in compat_mtw_from_user
Luxiao Xu says:
The function compat_mtw_from_user() converts ebtables extensions from 32-bit user structures to kernel native structures. However, it lacks proper validation of the user-supplied match_size/target_size.
When certain extensions are processed, the kernel-side translation logic may perform memory accesses based on the extension's expected size. If the user provides a size smaller than what the extension requires, it results in an out-of-bounds read as reported by KASAN.
This fix introduces a check to ensure match_size is at least as large as the extension's required compatsize. This covers matches, watchers, and targets, while maintaining compatibility with standard targets.
AFAIU this is relevant for matches that need to go though match->compat_from_user() call. Those that use plain memcpy with the user-provided size are ok because the caller checks that size vs the start of the next rule entry offset (which itself is checked vs. total size copied from userspace).
The ->compat_from_user() callbacks assume they can read compatsize bytes, so they need this extra check.
Based on an earlier patch from Luxiao Xu.
Weakness: CWE-125
Which versions are affected by CVE-2026-52927?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52927?
Apply the vendor's patch.
Is CVE-2026-52927 being exploited?
There is no known exploitation of CVE-2026-52927 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90765, BELL-CVE-2026-52927, DEBIAN-CVE-2026-52927, GHSA-c6h6-mmcc-x4qj, ROOT-OS-DEBIAN-11-CVE-2026-52927, ROOT-OS-DEBIAN-12-CVE-2026-52927 and 3 more.