# CVE-2026-89681: nfsd: fix layout fence worker double-reference race

> A race condition in the Linux kernel NFS server allows a double-reference leak, potentially leading to resource exhaustion and denial of service.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89681, GHSA-3x6w-r97p-5874, UBUNTU-CVE-2026-89681

## What is CVE-2026-89681?

CVE-2026-89681 is a critical vulnerability in Linux, published on 11 Sep 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:

nfsd: fix layout fence worker double-reference race

The workqueue core clears WORK_STRUCT_PENDING before the callback
is invoked, so delayed_work_pending() in lm_breaker_timedout() can
return false while the fence worker is already running. This lets
the breaker take a duplicate sc_count reference and schedule a new
worker that coalesces with the in-progress one. The extra reference
is never put, leaking the layout stateid.

Replace the racy delayed_work_pending() check with an
ls_fence_inflight boolean set atomically with
refcount_inc_not_zero() under ls_lock, and cleared under ls_lock
before the final nfs4_put_stid() on the dispose path; the retry
path intentionally retains it.  Remove the self-rearm
mod_delayed_work() at the top of the worker.

## Which versions are affected by CVE-2026-89681?


## How do I fix CVE-2026-89681?

Apply the vendor's patch.

## Is CVE-2026-89681 being exploited?

There is no known exploitation of CVE-2026-89681 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89681 and fix it if it is affected.

What it is: CVE-2026-89681 is a critical vulnerability in Linux, published on 11 Sep 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-2026-89681 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-2026-89681/ (Markdown: https://insights.sbomify.com/CVE-2026-89681/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89681
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89681
- OSV: https://osv.dev/vulnerability/CVE-2026-89681

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89681/
Summaries are generated and may contain mistakes; the official description above is the record.