# CVE-2021-40904: Code injection in n/a

> An administrator can achieve remote code execution by exploiting a default misconfiguration in the embedded Dokuwiki component of CheckMK Raw Edition.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 25 Mar 2022
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-f6hf-q5rw-f57w, UBUNTU-CVE-2021-40904

## What is CVE-2021-40904?

CVE-2021-40904 is a high-severity code injection vulnerability in Checkmk Checkmk, published on 25 Mar 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The web management console of CheckMK Raw Edition (versions 1.5.0 to 1.6.0) allows a misconfiguration of the web-app Dokuwiki (installed by default), which allows embedded php code. As a result, remote code execution is achieved. Successful exploitation requires access to the web management interface, either with valid credentials or with a hijacked session by a user with the role of administrator.

Weakness: CWE-276 (Incorrect Default Permissions)

## Which versions are affected by CVE-2021-40904?

It affects 1 product.


Products: Checkmk Checkmk.

## How do I fix CVE-2021-40904?

No fix has been published for CVE-2021-40904 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40904 being exploited?

There is no known exploitation of CVE-2021-40904 in the wild and no public exploit code.

Public exploit code:

- https://github.com/Edgarloyola/CVE-2021-40904 (github_poc): https://github.com/Edgarloyola/CVE-2021-40904

## Other vulnerabilities in Checkmk Checkmk

- [CVE-2025-39666](https://insights.sbomify.com/CVE-2025-39666/): omd: Local privilege escalation when executing omd commands as root (critical 9.3)
- [CVE-2024-8606](https://insights.sbomify.com/CVE-2024-8606/): Fix 2FA bypass via RestAPI (critical 9.2)
- [CVE-2022-46836](https://insights.sbomify.com/CVE-2022-46836/): PHP code injection in watolib (critical 9.1)
- [CVE-2025-32919](https://insights.sbomify.com/CVE-2025-32919/): Privilege Escalation in Windows License plugin for Checkmk Windows Agent (high 8.8)
- [CVE-2024-28827](https://insights.sbomify.com/CVE-2024-28827/): Privilege escalation in Windows agent (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40904 and fix it if it is affected.

What it is: CVE-2021-40904 is a high-severity code injection vulnerability in Checkmk Checkmk, published on 25 Mar 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-40904 in the wild and no public exploit code.

Affected product: Checkmk Checkmk. 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-2021-40904/ (Markdown: https://insights.sbomify.com/CVE-2021-40904/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40904
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40904
- OSV: https://osv.dev/vulnerability/CVE-2021-40904

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40904/
Summaries are generated and may contain mistakes; the official description above is the record.