# CVE-2025-39721: crypto: qat - flush misc workqueue during device shutdown

> A use-after-free in the Linux kernel QAT driver allows local attackers to cause a system crash by rapidly loading and unloading the driver.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 5 Sep 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-39721, DEBIAN-CVE-2025-39721, GHSA-c9qp-46j7-6qfj, ROOT-OS-DEBIAN-12-CVE-2025-39721, ROOT-OS-DEBIAN-13-CVE-2025-39721, ROOT-OS-UBUNTU-2404-CVE-2025-39721, UBUNTU-CVE-2025-39721

## What is CVE-2025-39721?

CVE-2025-39721 is a medium-severity use after free vulnerability in Linux kernel, published on 5 Sep 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:

crypto: qat - flush misc workqueue during device shutdown

Repeated loading and unloading of a device specific QAT driver, for
example qat_4xxx, in a tight loop can lead to a crash due to a
use-after-free scenario. This occurs when a power management (PM)
interrupt triggers just before the device-specific driver (e.g.,
qat_4xxx.ko) is unloaded, while the core driver (intel_qat.ko) remains
loaded.

Since the driver uses a shared workqueue (`qat_misc_wq`) across all
devices and owned by intel_qat.ko, a deferred routine from the
device-specific driver may still be pending in the queue. If this
routine executes after the driver is unloaded, it can dereference freed
memory, resulting in a page fault and kernel crash like the following:

    BUG: unable to handle page fault for address: ffa000002e50a01c
    #PF: supervisor read access in kernel mode
    RIP: 0010:pm_bh_handler+0x1d2/0x250 [intel_qat]
    Call Trace:
      pm_bh_handler+0x1d2/0x250 [intel_qat]
      process_one_work+0x171/0x340
      worker_thread+0x277/0x3a0
      kthread+0xf0/0x120
      ret_from_fork+0x2d/0x50

To prevent this, flush the misc workqueue during device shutdown to
ensure that all pending work items are completed before the driver is
unloaded.

Note: This approach may slightly increase shutdown latency if the
workqueue contains jobs from other devices, but it ensures correctness
and stability.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-39721?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39721?

Apply the vendor's patch.

## Is CVE-2025-39721 being exploited?

There is no known exploitation of CVE-2025-39721 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-2025-39721 and fix it if it is affected.

What it is: CVE-2025-39721 is a medium-severity use after free vulnerability in Linux kernel, published on 5 Sep 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-2025-39721 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-2025-39721/ (Markdown: https://insights.sbomify.com/CVE-2025-39721/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39721
- OSV: https://osv.dev/vulnerability/CVE-2025-39721

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39721/
Summaries are generated and may contain mistakes; the official description above is the record.