# CVE-2026-93212: nfsd: guard nfsd_serv deref in nfsd_file_net_dispose

> A null pointer dereference in the Linux kernel NFS server allows remote attackers to cause a denial of service during network namespace teardown.

- **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:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93212, DEBIAN-CVE-2026-93212, GHSA-8w8j-gj8p-wm2m, UBUNTU-CVE-2026-93212

## What is CVE-2026-93212?

CVE-2026-93212 is a vulnerability in Linux, published on 24 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: guard nfsd_serv deref in nfsd_file_net_dispose

nfsd_file_net_dispose() is the consumer side of l->freeme: the nfsd
service thread loop calls it to drain entries that the filecache
garbage collector and shrinker append via
nfsd_file_dispose_list_delayed().  During per-net teardown,
nn->nfsd_serv is cleared before the filecache laundrette is shut
down, so the service thread can still run a dispose pass that finds
more than eight entries on l->freeme and dereferences a NULL
svc_serv:

    nfsd service thread loop
      nfsd_file_net_dispose(nn)
        if (!list_empty(&l->freeme)) {
            ...
            svc_wake_up(nn->nfsd_serv);   /* nn->nfsd_serv == NULL */
        }

The sibling helper nfsd_file_dispose_list_delayed() already documents
this ordering and caches nn->nfsd_serv into a local before testing it
for NULL.  nfsd_file_net_dispose() was introduced with the same raw
svc_wake_up(nn->nfsd_serv) call and never picked up the guard.

Fix by loading nn->nfsd_serv into a local svc_serv pointer and only
calling svc_wake_up() when it is non-NULL, matching the pattern in
nfsd_file_dispose_list_delayed().

## Which versions are affected by CVE-2026-93212?


## How do I fix CVE-2026-93212?

Apply the vendor's patch.

## Is CVE-2026-93212 being exploited?

There is no known exploitation of CVE-2026-93212 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93212 and fix it if it is affected.

What it is: CVE-2026-93212 is a vulnerability in Linux, published on 24 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-2026-93212 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-2026-93212/ (Markdown: https://insights.sbomify.com/CVE-2026-93212/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93212
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93212
- OSV: https://osv.dev/vulnerability/CVE-2026-93212

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93212/
Summaries are generated and may contain mistakes; the official description above is the record.