CVE-2026-72436 netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types
A race condition in Linux kernel ipset hash types due to missing memory barriers in lockless RCU readers could lead to undefined behavior.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72436?
CVE-2026-72436 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types
Sashiko pointed out that there are a few lockless RCU readers using test_bit() which is a relaxed atomic operation and provides no memory barrier guarantees. Use test_bit_acquire() instead where the operation may run parallel with add/del/gc, i.e. is not one from the next cases
- protected by region lock - in a set destroy phase - in a new/temporary set creation phase
Which versions are affected by CVE-2026-72436?
How do I fix CVE-2026-72436?
Apply the vendor's patch.
Is CVE-2026-72436 being exploited?
There is no known exploitation of CVE-2026-72436 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72436, DEBIAN-CVE-2026-72436, GHSA-6x4x-6p4p-6f5f, UBUNTU-CVE-2026-72436.