# CVE-2026-89705: nfsd: restore rq_status_counter to even on all nfsd_dispatch() exit paths

> A race condition in the Linux kernel NFS server allows a lockless reader to access mutating fields, potentially causing out-of-bounds reads and system instability.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-89705, DEBIAN-CVE-2026-89705, GHSA-pvqx-hghh-c66m, UBUNTU-CVE-2026-89705

## What is CVE-2026-89705?

CVE-2026-89705 is a high-severity vulnerability in Linux, published on 11 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:

nfsd: restore rq_status_counter to even on all nfsd_dispatch() exit paths

nfsd_dispatch() sets rq_status_counter to an odd value once a request has
been decoded, and back to an even value once it has been fully processed,
forming a seq-lock like protocol with the lockless reader in
nfsd_nl_rpc_status_get_dumpit().

Only the fully successful path restored the counter to even. The cache-hit
(RC_REPLY), drop (RC_DROPIT / RQ_DROPME) and encode-error paths all return
after the odd-valued store without ever bringing the counter back to even.
Once one of those paths is taken, rq_status_counter is left odd: the next
request's decode ORs in 1 (still odd) and only a subsequent successful
encode restores even. While stuck odd, the dumpit reader treats the rqstp
fields as stable and its retry check compares against the same unchanging
odd value, so it never detects concurrent mutation. This exposes actively
mutating fields (e.g. args->ops / args->opcnt during compound decode and
release) to the lockless reader, which can read past the end of the
8-element inline ops array.

Add a helper that advances the counter to the next even value and call it
on every return path that follows the odd-valued store. The decode-error
path is left untouched as it is reached before the counter is set odd.

## Which versions are affected by CVE-2026-89705?


## How do I fix CVE-2026-89705?

Apply the vendor's patch.

## Is CVE-2026-89705 being exploited?

There is no known exploitation of CVE-2026-89705 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89705 and fix it if it is affected.

What it is: CVE-2026-89705 is a high-severity vulnerability in Linux, published on 11 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-2026-89705 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-2026-89705/ (Markdown: https://insights.sbomify.com/CVE-2026-89705/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89705
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89705
- OSV: https://osv.dev/vulnerability/CVE-2026-89705

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89705/
Summaries are generated and may contain mistakes; the official description above is the record.