# CVE-2026-93261: locking/lockdep: Fix NULL pointer dereference in __lock_set_class()

> A NULL pointer dereference in the Linux kernel lockdep subsystem can cause a system crash when the lock class pool is exhausted.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93261, DEBIAN-CVE-2026-93261, GHSA-mh76-8wxp-345h, UBUNTU-CVE-2026-93261

## What is CVE-2026-93261?

CVE-2026-93261 is a vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

locking/lockdep: Fix NULL pointer dereference in __lock_set_class()

register_lock_class() can return NULL when the lock class pool is
exhausted, graph_lock() fails, or key validation fails. However,
__lock_set_class() uses the return value directly in pointer arithmetic
without a NULL check:

  class = register_lock_class(lock, subclass, 0);
  hlock->class_idx = class - lock_classes;

If class is NULL, this computes a wild offset that corrupts
hlock->class_idx. The subsequent reacquire_held_locks() call will
invoke hlock_class() with this corrupted index, leading to a NULL or
out-of-bounds pointer dereference.

Add the missing NULL check, consistent with how __lock_acquire() already
handles this case at the same call site.

## Which versions are affected by CVE-2026-93261?


## How do I fix CVE-2026-93261?

Apply the vendor's patch.

## Is CVE-2026-93261 being exploited?

There is no known exploitation of CVE-2026-93261 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93261 and fix it if it is affected.

What it is: CVE-2026-93261 is a vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-93261 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-2026-93261/ (Markdown: https://insights.sbomify.com/CVE-2026-93261/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93261
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93261
- OSV: https://osv.dev/vulnerability/CVE-2026-93261

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93261/
Summaries are generated and may contain mistakes; the official description above is the record.