# 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.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102417, BELL-CVE-2026-90061, DEBIAN-CVE-2026-90061, GHSA-gc4j-f8fc-95gw, UBUNTU-CVE-2026-90061

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90061 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-90061 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-90061/ (Markdown: https://insights.sbomify.com/CVE-2026-90061/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90061
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90061
- OSV: https://osv.dev/vulnerability/CVE-2026-90061

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90061/
Summaries are generated and may contain mistakes; the official description above is the record.