CVE-2026-80636 netfilter: conntrack: revert ct extension genid infrastructure
A null pointer dereference in the Linux kernel netfilter conntrack subsystem allows remote attackers to cause a system crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80636?
CVE-2026-80636 is a vulnerability in Linux, published on 28 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: conntrack: revert ct extension genid infrastructure
This infrastructure is not used anymore after moving ct timeout and helper to use datapath refcount to track object use.
Revert commit c56716c69ce1 ("netfilter: extensions: introduce extension genid count") this patch disables all ct extensions (leading to NULL) for unconfirmed conntracks, when this is only targeted at ct helper and ct timeout. There is also codebase that dereferences the ct extension without checking for NULL which could lead to crash.
Which versions are affected by CVE-2026-80636?
How do I fix CVE-2026-80636?
Apply the vendor's patch.
Is CVE-2026-80636 being exploited?
There is no known exploitation of CVE-2026-80636 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-80636, DEBIAN-CVE-2026-80636, GHSA-xc67-x6qc-f6hf, UBUNTU-CVE-2026-80636.