# CVE-2026-74347: netfilter: cttimeout: detach dataplane timeout policy and repurpose refcount

> A use-after-free vulnerability in the Linux kernel netfilter subsystem allows attackers to execute arbitrary code or escalate privileges via crafted network traffic.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-96567, BELL-CVE-2026-74347, DEBIAN-CVE-2026-74347, GHSA-7mmw-w232-r226, UBUNTU-CVE-2026-74347

## What is CVE-2026-74347?

CVE-2026-74347 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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: cttimeout: detach dataplane timeout policy and repurpose refcount

Add a refcount for struct nf_ct_timeout which is used by ct extension to
set the custom ct timeout policy, this tells us that the ct timeout is
being used by a conntrack entry. When the last conntrack entry drops the
refcount on the ct timeout, the ct timeout is released.

Remove the refcount for control plane which controls if the ruleset
refers to the timeout policy. After this update, it is possible to
remove the ct timeout policy from nfnetlink_cttimeout immediately.
This is for simplicity not to handle two refcounts on a single object.

Remove nf_queue_nf_hook_drop(): a packet sitting in nfqueue will just
hold a reference to the nf_ct_timeout object until packet is reinjected,
since this is part of the ct extension, this will be released by the
time the conntrack is freed.

nf_ct_untimeout() is still called to clean up in a best effort basis:
the ct timeout on existing entries gets removed when the ct timeout goes
away, but as long as the iptables ruleset still refers to the ct timeout
through a template, new conntracks may keep attaching it and extend its
lifetime until the rule is removed.

nf_ct_untimeout() is not called anymore from module removal path, this
is unlikely to find timeouts give module refcount is bumped, and the new
refcount already tracks the ct timeout policy use so it is released when
unused.

## Which versions are affected by CVE-2026-74347?


## How do I fix CVE-2026-74347?

Apply the vendor's patch.

## Is CVE-2026-74347 being exploited?

There is no known exploitation of CVE-2026-74347 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74347 and fix it if it is affected.

What it is: CVE-2026-74347 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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-2026-74347 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-2026-74347/ (Markdown: https://insights.sbomify.com/CVE-2026-74347/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74347
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74347
- OSV: https://osv.dev/vulnerability/CVE-2026-74347

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74347/
Summaries are generated and may contain mistakes; the official description above is the record.