# CVE-2026-74401: dlm: fix add msg handle in send_queue ordered

> A race condition in the Linux kernel Distributed Lock Manager can lead to use-after-free, potentially allowing local attackers to execute code or escalate privileges.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74401, DEBIAN-CVE-2026-74401, GHSA-wgc9-j6gh-934m, UBUNTU-CVE-2026-74401

## What is CVE-2026-74401?

CVE-2026-74401 is a critical use after free 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:

dlm: fix add msg handle in send_queue ordered

In a benchmark scenario triggering a lot of requests that triggers a lot
of DLM messages on the network it can be that the mh->seq is not ordered
according the oldest seq number. This ordering is required by
dlm_receive_ack as "before(mh->seq, seq)" will stop to check for older
sequence numbers that are ordered in the tail of "node->send_queue".

The side effects of not having it correct ordered regarding
"before(mh->seq, seq)" are refcounting issues and use-after free.

I only was able to reproduce this issue in a experimental DLM branch
and a user space DLM benchmark that uses io_uring. After changing this I
don't experienced any refcounting with the sending buffer issues anymore.

## Which versions are affected by CVE-2026-74401?


## How do I fix CVE-2026-74401?

Apply the vendor's patch.

## Is CVE-2026-74401 being exploited?

There is no known exploitation of CVE-2026-74401 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74401 and fix it if it is affected.

What it is: CVE-2026-74401 is a critical use after free 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.
Exploitation: There is no known exploitation of CVE-2026-74401 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-2026-74401/ (Markdown: https://insights.sbomify.com/CVE-2026-74401/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74401
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74401
- OSV: https://osv.dev/vulnerability/CVE-2026-74401

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74401/
Summaries are generated and may contain mistakes; the official description above is the record.