# CVE-2026-89684: nfsd: fix cpntf publish race in nfs4_init_cp_state

> A race condition in the Linux kernel NFS server allows a remote attacker to cause a system crash via a crafted OFFLOAD_CANCEL request.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** AZL-100653, BELL-CVE-2026-89684, DEBIAN-CVE-2026-89684, GHSA-83g2-j7m2-94hx, UBUNTU-CVE-2026-89684

## What is CVE-2026-89684?

CVE-2026-89684 is a high-severity 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 cpntf publish race in nfs4_init_cp_state

nfs4_alloc_init_cpntf_state() published the new cpntf entry into the
s2s_cp_stateids IDR (with cs_type set) in one s2s_cp_lock section, then
took the lock again to list_add() it onto p_stid->sc_cp_list. In the gap
the entry is reachable by so_id but cp_list is still {NULL,NULL} from
kzalloc. A racing OFFLOAD_CANCEL (so_id is echoed to the client as
cnr_stateid, so any NFSv4.2 client can drive it) reaches
manage_cpntf_state() -> _free_cpntf_state_locked() and does list_del() on
the zeroed list_head, oopsing the server.

Fold the cs_type assignment and the list_add() into the same critical
section as idr_alloc_cyclic(), so a concurrent lookup either misses the
entry or sees a fully linked cp_list. INIT_LIST_HEAD() the entry after
allocation and switch _free_cpntf_state_locked() to list_del_init() so a
stale unlink is a no-op. nfs4_init_copy_state() passes NULL p_stid and
skips the list_add, preserving NFS4_COPY_STID semantics.

## Which versions are affected by CVE-2026-89684?


## How do I fix CVE-2026-89684?

Apply the vendor's patch.

## Is CVE-2026-89684 being exploited?

There is no known exploitation of CVE-2026-89684 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89684 and fix it if it is affected.

What it is: CVE-2026-89684 is a high-severity 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-2026-89684 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-2026-89684/ (Markdown: https://insights.sbomify.com/CVE-2026-89684/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89684
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89684
- OSV: https://osv.dev/vulnerability/CVE-2026-89684

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89684/
Summaries are generated and may contain mistakes; the official description above is the record.