# CVE-2025-21786: workqueue: Put the pwq after detaching the rescuer from the pool

> A use-after-free vulnerability in the Linux kernel workqueue subsystem allows attackers to execute arbitrary code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Feb 2025
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-58887, AZL-58922, BELL-CVE-2025-21786, DEBIAN-CVE-2025-21786, GHSA-jfr9-726h-gv8r, ROOT-OS-UBUNTU-2204-CVE-2025-21786, ROOT-OS-UBUNTU-2404-CVE-2025-21786, UBUNTU-CVE-2025-21786

## What is CVE-2025-21786?

CVE-2025-21786 is a high-severity use after free vulnerability in Linux kernel, published on 27 Feb 2025. 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:

workqueue: Put the pwq after detaching the rescuer from the pool

The commit 68f83057b913("workqueue: Reap workers via kthread_stop() and
remove detach_completion") adds code to reap the normal workers but
mistakenly does not handle the rescuer and also removes the code waiting
for the rescuer in put_unbound_pool(), which caused a use-after-free bug
reported by Cheung Wall.

To avoid the use-after-free bug, the pool’s reference must be held until
the detachment is complete. Therefore, move the code that puts the pwq
after detaching the rescuer from the pool.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-21786?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21786?

Apply the vendor's patch.

## Is CVE-2025-21786 being exploited?

There is no known exploitation of CVE-2025-21786 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-2025-21786 and fix it if it is affected.

What it is: CVE-2025-21786 is a high-severity use after free vulnerability in Linux kernel, published on 27 Feb 2025. 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-2025-21786 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-2025-21786/ (Markdown: https://insights.sbomify.com/CVE-2025-21786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21786
- OSV: https://osv.dev/vulnerability/CVE-2025-21786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21786/
Summaries are generated and may contain mistakes; the official description above is the record.