# CVE-2026-89683: nfsd: fix dentry ref leak on V4ROOT export filehandle lookup

> A crafted NFSv3 filehandle targeting a V4ROOT export causes a dentry reference leak, leading to resource exhaustion and denial of service.

- **Severity:** Not scored
- **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:** BELL-CVE-2026-89683, DEBIAN-CVE-2026-89683, GHSA-58hv-jwv2-hff3, UBUNTU-CVE-2026-89683

## What is CVE-2026-89683?

CVE-2026-89683 is a denial of service 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 dentry ref leak on V4ROOT export filehandle lookup

nfsd_set_fh_dentry() leaks the dentry reference from
exportfs_decode_fh_raw() when the NFS3_FHSIZE or NFS_FHSIZE
switch cases detect NFSEXP_V4ROOT and goto out. The out: label
calls exp_put() but never dput(dentry), and fhp->fh_dentry was
never assigned so fh_put() cannot compensate.

A crafted NFSv3 filehandle targeting a V4ROOT export's fsid
triggers the leak on every request.

## Which versions are affected by CVE-2026-89683?


## How do I fix CVE-2026-89683?

Apply the vendor's patch.

## Is CVE-2026-89683 being exploited?

There is no known exploitation of CVE-2026-89683 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89683 and fix it if it is affected.

What it is: CVE-2026-89683 is a denial of service 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-2026-89683 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-2026-89683/ (Markdown: https://insights.sbomify.com/CVE-2026-89683/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89683
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89683
- OSV: https://osv.dev/vulnerability/CVE-2026-89683

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89683/
Summaries are generated and may contain mistakes; the official description above is the record.