# CVE-2025-39994: media: tuner: xc5000: Fix use-after-free in xc5000_release

> A use-after-free vulnerability in the Linux kernel's xc5000 tuner driver allows attackers to potentially execute code or escalate privileges via a race condition.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Oct 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-68510, BELL-CVE-2025-39994, DEBIAN-CVE-2025-39994, GHSA-ghgh-r6c5-cgx8, ROOT-OS-DEBIAN-11-CVE-2025-39994, ROOT-OS-DEBIAN-12-CVE-2025-39994, ROOT-OS-DEBIAN-13-CVE-2025-39994, ROOT-OS-UBUNTU-2204-CVE-2025-39994, ROOT-OS-UBUNTU-2404-CVE-2025-39994, UBUNTU-CVE-2025-39994

## What is CVE-2025-39994?

CVE-2025-39994 is a high-severity use after free vulnerability in Linux, published on 15 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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

media: tuner: xc5000: Fix use-after-free in xc5000_release

The original code uses cancel_delayed_work() in xc5000_release(), which
does not guarantee that the delayed work item timer_sleep has fully
completed if it was already running. This leads to use-after-free scenarios
where xc5000_release() may free the xc5000_priv while timer_sleep is still
active and attempts to dereference the xc5000_priv.

A typical race condition is illustrated below:

CPU 0 (release thread)                 | CPU 1 (delayed work callback)
xc5000_release()                       | xc5000_do_timer_sleep()
  cancel_delayed_work()                |
  hybrid_tuner_release_state(priv)     |
    kfree(priv)                        |
                                       |   priv = container_of() // UAF

Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure
that the timer_sleep is properly canceled before the xc5000_priv memory
is deallocated.

A deadlock concern was considered: xc5000_release() is called in a process
context and is not holding any locks that the timer_sleep work item might
also need. Therefore, the use of the _sync() variant is safe here.

This bug was initially identified through static analysis.

[hverkuil: fix typo in Subject: tunner -> tuner]

## Which versions are affected by CVE-2025-39994?


## How do I fix CVE-2025-39994?

Apply the vendor's patch.

## Is CVE-2025-39994 being exploited?

There is no known exploitation of CVE-2025-39994 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39994 and fix it if it is affected.

What it is: CVE-2025-39994 is a high-severity use after free vulnerability in Linux, published on 15 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-39994 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-2025-39994/ (Markdown: https://insights.sbomify.com/CVE-2025-39994/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39994
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39994
- OSV: https://osv.dev/vulnerability/CVE-2025-39994

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39994/
Summaries are generated and may contain mistakes; the official description above is the record.