# CVE-2026-90038: NFSD: Prevent client use-after-free during export state revocation

> A use-after-free in the Linux kernel NFSD module allows attackers to cause denial of service or execute code during export state revocation.

- **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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** GHSA-j297-c8rv-68vc, UBUNTU-CVE-2026-90038

## What is CVE-2026-90038?

CVE-2026-90038 is a critical use after free vulnerability in Linux, published on 16 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: Prevent client use-after-free during export state revocation

nfsd4_revoke_export_states() has the same use-after-free as
nfsd4_revoke_states(): it drops nn->client_lock across
revoke_one_stid() and the following read of clp->cl_minorversion, but
the stateid reference it holds does not pin the client.  A teardown
racing the dropped lock can free the client while revoke_one_stid()
still dereferences it.

exportfs -u drives this path through NFSD_CMD_UNLOCK_EXPORT, so an
administrator removing an export can race a client expiry.

Skip a client that is already expiring and otherwise pin it with
cl_rpc_users under client_lock before dropping the lock, matching
nfsd4_revoke_states().

## Which versions are affected by CVE-2026-90038?


## How do I fix CVE-2026-90038?

Apply the vendor's patch.

## Is CVE-2026-90038 being exploited?

There is no known exploitation of CVE-2026-90038 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90038 and fix it if it is affected.

What it is: CVE-2026-90038 is a critical use after free vulnerability in Linux, published on 16 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-2026-90038 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-2026-90038/ (Markdown: https://insights.sbomify.com/CVE-2026-90038/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90038
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90038
- OSV: https://osv.dev/vulnerability/CVE-2026-90038

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90038/
Summaries are generated and may contain mistakes; the official description above is the record.