# CVE-2025-40021: tracing: dynevent: Add a missing lockdown check on dynevent

> Attackers with high privileges can bypass kernel lockdown restrictions via the dynamic events interface in the Linux kernel.

- **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:** 24 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-68811, BELL-CVE-2025-40021, DEBIAN-CVE-2025-40021, GHSA-hmw5-3qc9-5j9m, ROOT-OS-DEBIAN-11-CVE-2025-40021, ROOT-OS-UBUNTU-2404-CVE-2025-40021, UBUNTU-CVE-2025-40021

## What is CVE-2025-40021?

CVE-2025-40021 is a vulnerability in Linux, published on 24 Oct 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:

tracing: dynevent: Add a missing lockdown check on dynevent

Since dynamic_events interface on tracefs is compatible with
kprobe_events and uprobe_events, it should also check the lockdown
status and reject if it is set.

## Which versions are affected by CVE-2025-40021?


## How do I fix CVE-2025-40021?

Apply the vendor's patch.

## Is CVE-2025-40021 being exploited?

There is no known exploitation of CVE-2025-40021 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40021 and fix it if it is affected.

What it is: CVE-2025-40021 is a vulnerability in Linux, published on 24 Oct 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-2025-40021 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-2025-40021/ (Markdown: https://insights.sbomify.com/CVE-2025-40021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40021
- OSV: https://osv.dev/vulnerability/CVE-2025-40021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40021/
Summaries are generated and may contain mistakes; the official description above is the record.