CVE-2026-90061 netfilter: nf_tables: skip double clone set expressions on element insert
A double clone bug in Linux kernel netfilter nf_tables causes a module refcount imbalance and kernel warning, potentially leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90061?
CVE-2026-90061 is a vulnerability in Linux, published on 17 Sep 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: nf_tables: skip double clone set expressions on element insert
Both the dynset and newsetelem path clone the existing set expressions when setting set element expressions if no override expressions are provided. This results in a double clone, once to clone the template set expressions then another clone on the new element. Add a flag to annotate if userspace provides a override expression (ie. expression of the same type of the set but different configuration), otherwise borrow the existing expression from the set. Add conditionals to release expression iif they represent an override. Use this new override_exprs flag to dump the dynset expression override to userspace.
This simplifies the existing logic and it also fixes a bug with the connlimit expression which results in a module refcount imbalance WARNING splat when resorting on the default set expressions.
Which versions are affected by CVE-2026-90061?
How do I fix CVE-2026-90061?
Apply the vendor's patch.
Is CVE-2026-90061 being exploited?
There is no known exploitation of CVE-2026-90061 in the wild and no public exploit code.
Sources
Also known as AZL-102417, BELL-CVE-2026-90061, DEBIAN-CVE-2026-90061, GHSA-gc4j-f8fc-95gw, UBUNTU-CVE-2026-90061.