# CVE-2026-89709: lockd, nfsd: RCU-protect nlmsvc_ops dispatch

> A race condition in the Linux kernel's lockd/nfsd module can lead to use-after-free or null dereference, potentially causing crashes or code execution.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/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:** 21 Oct 2026
- **Also known as:** AZL-100898, BELL-CVE-2026-89709, DEBIAN-CVE-2026-89709, GHSA-g58f-8h46-hjgv, UBUNTU-CVE-2026-89709

## What is CVE-2026-89709?

CVE-2026-89709 is a high-severity use after free 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:

lockd, nfsd: RCU-protect nlmsvc_ops dispatch

nlmsvc_ops is published by nfsd_lockd_init() and cleared by
nfsd_lockd_shutdown() with plain stores, while lockd dereferences
it unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer
targets nfsd's .rodata and the fopen/fclose callbacks live in nfsd's
.text, so a stale load after rmmod nfsd results in either a NULL
deref or a module-text use-after-free.

Declare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear
via RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module
*owner field to nlmsvc_binding and pin the module across indirect
calls with try_module_get/module_put. When the binding is torn down,
fall back to fput() to avoid leaking struct file references.

## Which versions are affected by CVE-2026-89709?


## How do I fix CVE-2026-89709?

Apply the vendor's patch.

## Is CVE-2026-89709 being exploited?

There is no known exploitation of CVE-2026-89709 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89709 and fix it if it is affected.

What it is: CVE-2026-89709 is a high-severity use after free 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-2026-89709 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-2026-89709/ (Markdown: https://insights.sbomify.com/CVE-2026-89709/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89709
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89709
- OSV: https://osv.dev/vulnerability/CVE-2026-89709

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89709/
Summaries are generated and may contain mistakes; the official description above is the record.