# CVE-2025-39688: nfsd: allow SC_STATUS_FREEABLE when searching via nfs4_lookup_stateid()

> A logic error in the Linux kernel NFS server causes revoked delegations to be mishandled, potentially leading to denial of service.

- **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:** 18 Apr 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-39688, DEBIAN-CVE-2025-39688, GHSA-53x5-v4j3-g5xm, UBUNTU-CVE-2025-39688

## What is CVE-2025-39688?

CVE-2025-39688 is a high-severity denial of service vulnerability in Linux kernel, published on 18 Apr 2025. 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: allow SC_STATUS_FREEABLE when searching via nfs4_lookup_stateid()

The pynfs DELEG8 test fails when run against nfsd. It acquires a
delegation and then lets the lease time out. It then tries to use the
deleg stateid and expects to see NFS4ERR_DELEG_REVOKED, but it gets
bad NFS4ERR_BAD_STATEID instead.

When a delegation is revoked, it's initially marked with
SC_STATUS_REVOKED, or SC_STATUS_ADMIN_REVOKED and later, it's marked
with the SC_STATUS_FREEABLE flag, which denotes that it is waiting for
s FREE_STATEID call.

nfs4_lookup_stateid() accepts a statusmask that includes the status
flags that a found stateid is allowed to have. Currently, that mask
never includes SC_STATUS_FREEABLE, which means that revoked delegations
are (almost) never found.

Add SC_STATUS_FREEABLE to the always-allowed status flags, and remove it
from nfsd4_delegreturn() since it's now always implied.

## Which versions are affected by CVE-2025-39688?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39688?

Apply the vendor's patch.

## Is CVE-2025-39688 being exploited?

There is no known exploitation of CVE-2025-39688 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39688 and fix it if it is affected.

What it is: CVE-2025-39688 is a high-severity denial of service vulnerability in Linux kernel, published on 18 Apr 2025. 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-2025-39688 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-39688/ (Markdown: https://insights.sbomify.com/CVE-2025-39688/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39688
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39688
- OSV: https://osv.dev/vulnerability/CVE-2025-39688

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39688/
Summaries are generated and may contain mistakes; the official description above is the record.