# CVE-2025-40228: mm/damon/sysfs: catch commit test ctx alloc failure

> A missing allocation check in the Linux kernel DAMON sysfs interface can lead to invalid memory access and system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40228, DEBIAN-CVE-2025-40228, GHSA-2g63-4p26-m2f6, UBUNTU-CVE-2025-40228

## What is CVE-2025-40228?

CVE-2025-40228 is a vulnerability in Linux, published on 4 Dec 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:

mm/damon/sysfs: catch commit test ctx alloc failure

Patch series "mm/damon/sysfs: fix commit test damon_ctx [de]allocation".

DAMON sysfs interface dynamically allocates and uses a damon_ctx object
for testing if given inputs for online DAMON parameters update is valid.
The object is being used without an allocation failure check, and leaked
when the test succeeds.  Fix the two bugs.

This patch (of 2):

The damon_ctx for testing online DAMON parameters commit inputs is used
without its allocation failure check.  This could result in an invalid
memory access.  Fix it by directly returning an error when the allocation
failed.

## Which versions are affected by CVE-2025-40228?


## How do I fix CVE-2025-40228?

Apply the vendor's patch.

## Is CVE-2025-40228 being exploited?

There is no known exploitation of CVE-2025-40228 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40228 and fix it if it is affected.

What it is: CVE-2025-40228 is a vulnerability in Linux, published on 4 Dec 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-2025-40228 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-2025-40228/ (Markdown: https://insights.sbomify.com/CVE-2025-40228/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40228
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40228
- OSV: https://osv.dev/vulnerability/CVE-2025-40228

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40228/
Summaries are generated and may contain mistakes; the official description above is the record.