# CVE-2025-40211: ACPI: video: Fix use-after-free in acpi_video_switch_brightness()

> A use-after-free in the Linux kernel ACPI video driver allows local attackers to execute arbitrary code or escalate privileges.

- **Severity:** Not scored
- **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:** 21 Nov 2025
- **Updated:** 16 Jun 2026
- **Also known as:** AZL-70657, BELL-CVE-2025-40211, DEBIAN-CVE-2025-40211, GHSA-3xv8-84fj-hhg4, ROOT-OS-DEBIAN-11-CVE-2025-40211, ROOT-OS-DEBIAN-12-CVE-2025-40211, ROOT-OS-DEBIAN-13-CVE-2025-40211, ROOT-OS-UBUNTU-2204-CVE-2025-40211, ROOT-OS-UBUNTU-2404-CVE-2025-40211, UBUNTU-CVE-2025-40211

## What is CVE-2025-40211?

CVE-2025-40211 is an use after free vulnerability in Linux, published on 21 Nov 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:

ACPI: video: Fix use-after-free in acpi_video_switch_brightness()

The switch_brightness_work delayed work accesses device->brightness
and device->backlight, freed by acpi_video_dev_unregister_backlight()
during device removal.

If the work executes after acpi_video_bus_unregister_backlight()
frees these resources, it causes a use-after-free when
acpi_video_switch_brightness() dereferences device->brightness or
device->backlight.

Fix this by calling cancel_delayed_work_sync() for each device's
switch_brightness_work in acpi_video_bus_remove_notify_handler()
after removing the notify handler that queues the work. This ensures
the work completes before the memory is freed.

[ rjw: Changelog edit ]

## Which versions are affected by CVE-2025-40211?


## How do I fix CVE-2025-40211?

Apply the vendor's patch.

## Is CVE-2025-40211 being exploited?

There is no known exploitation of CVE-2025-40211 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40211 and fix it if it is affected.

What it is: CVE-2025-40211 is an use after free vulnerability in Linux, published on 21 Nov 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-2025-40211 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-2025-40211/ (Markdown: https://insights.sbomify.com/CVE-2025-40211/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40211
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40211
- OSV: https://osv.dev/vulnerability/CVE-2025-40211

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40211/
Summaries are generated and may contain mistakes; the official description above is the record.