# CVE-2021-41039: Denial of service in Eclipse Mosquitto

> An attacker can cause excessive CPU usage and potential denial of service in Eclipse Mosquitto by sending an MQTT v5 client connection with many user-property properties.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-41039, GHSA-5xp2-36v8-r67m, OESA-2022-1498, UBUNTU-CVE-2021-41039

## What is CVE-2021-41039?

CVE-2021-41039 is a high-severity denial of service vulnerability in The Eclipse Foundation Eclipse Mosquitto, published on 1 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Weakness: CWE-1050 (Excessive Platform Resource Consumption within a Loop)

## Which versions are affected by CVE-2021-41039?

It affects 1 product.


Products: Eclipse Mosquitto.

## How do I fix CVE-2021-41039?

Upgrade to a fixed version.

## Is CVE-2021-41039 being exploited?

There is no known exploitation of CVE-2021-41039 in the wild and no public exploit code.

## Other vulnerabilities in The Eclipse Foundation Eclipse Mosquitto

- [CVE-2018-12550](https://insights.sbomify.com/CVE-2018-12550/): Auth bypass in Eclipse Mosquitto (high 8.1)
- [CVE-2018-12551](https://insights.sbomify.com/CVE-2018-12551/): Auth bypass in Eclipse Mosquitto (high 8.1)
- [CVE-2023-5632](https://insights.sbomify.com/CVE-2023-5632/): Unconditionally adding an event to the epoll causes excessive CPU consumption (high 7.5)
- [CVE-2023-28366](https://insights.sbomify.com/CVE-2023-28366/): Denial of service in n/a (high 7.5)
- [CVE-2021-34432](https://insights.sbomify.com/CVE-2021-34432/): Denial of service in Eclipse Mosquitto (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41039 and fix it if it is affected.

What it is: CVE-2021-41039 is a high-severity denial of service vulnerability in The Eclipse Foundation Eclipse Mosquitto, published on 1 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-41039 in the wild and no public exploit code.

Affected product: The Eclipse Foundation Eclipse Mosquitto. 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-2021-41039/ (Markdown: https://insights.sbomify.com/CVE-2021-41039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41039
- OSV: https://osv.dev/vulnerability/CVE-2021-41039

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-41039/
Summaries are generated and may contain mistakes; the official description above is the record.