# CVE-2026-89687: nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file

> A flaw in the Linux kernel NFS server could lead to a null pointer dereference if a file is not properly opened, causing a 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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89687, GHSA-vpqx-gvmc-m7vf, UBUNTU-CVE-2026-89687

## What is CVE-2026-89687?

CVE-2026-89687 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: ensure nfsd_file_do_acquire() does not use a non-opened file

->atomic_open is permitted to return success without actually opening
the file.  It indicates this by calling finish_no_open().
This means dentry_create() can return a file which hasn't been opened.
This is extremely unlikely as ->atomic_open handlers typically
use finish_no_open() only for already existing files, and dentry_create()
isn't called in that case, and the parent being locked should prevent
races.

However out of an abundance of caution it seems wise to teach nfsd to
only use the file returned by dentry_create() if FMODE_OPENED is set,
indicating that it has in fact been opened.

## Which versions are affected by CVE-2026-89687?


## How do I fix CVE-2026-89687?

Apply the vendor's patch.

## Is CVE-2026-89687 being exploited?

There is no known exploitation of CVE-2026-89687 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89687 and fix it if it is affected.

What it is: CVE-2026-89687 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-2026-89687 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-2026-89687/ (Markdown: https://insights.sbomify.com/CVE-2026-89687/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89687
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89687
- OSV: https://osv.dev/vulnerability/CVE-2026-89687

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89687/
Summaries are generated and may contain mistakes; the official description above is the record.