# CVE-2021-4040: org.apache.activemq:artemis-core-client Vulnerable to Out-of-Bounds Write

> An attacker can cause a partial denial of service in AMQ Broker by sending maliciously crafted messages that trigger an out-of-memory condition.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-gf8c-j759-86mg

## What is CVE-2021-4040?

CVE-2021-4040 is a medium-severity denial of service vulnerability in AMQ Broker, published on 24 Aug 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in AMQ Broker. This issue can cause a partial interruption to the availability of AMQ Broker via an Out of memory (OOM) condition. This flaw allows an attacker to partially disrupt availability to the broker through a sustained attack of maliciously crafted messages. The highest threat from this vulnerability is system availability.

Weakness: CWE-787 (Out-of-bounds Write), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-4040?

2 open source packages ship an affected version, including org.apache.activemq:artemis-core-client. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.activemq:artemis-core-client` | Maven | All versions | 2.19.1 |
| `org.apache.activemq:artemis-core-client` | Maven | All versions | 2.19.1 |

Products: Apache Artemis, Redhat Amq Broker.

## How do I fix CVE-2021-4040?

Upgrade org.apache.activemq:artemis-core-client to 2.19.1 or later.

## Is CVE-2021-4040 being exploited?

There is no known exploitation of CVE-2021-4040 in the wild and no public exploit code.

## Other vulnerabilities in AMQ Broker

- [CVE-2026-57967](https://insights.sbomify.com/CVE-2026-57967/): Apache Artemis, Apache ActiveMQ Artemis: Missing authentication on CORE protocol session reattachment (critical 9.8)
- [CVE-2026-27446](https://insights.sbomify.com/CVE-2026-27446/): Apache Artemis, Apache ActiveMQ Artemis: Auth bypass for Core downstream federation (critical 9.3)
- [CVE-2026-49364](https://insights.sbomify.com/CVE-2026-49364/): Information disclosure in Apache ActiveMQ Artemis (critical 9.1)
- [CVE-2026-67593](https://insights.sbomify.com/CVE-2026-67593/): Missing authorization in Apache ActiveMQ Artemis (critical 9.1)
- [CVE-2023-50780](https://insights.sbomify.com/CVE-2023-50780/): Apache ActiveMQ Artemis: Authenticated users could perform RCE via Jolokia MBeans (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4040 and fix it if it is affected.

What it is: CVE-2021-4040 is a medium-severity denial of service vulnerability in AMQ Broker, published on 24 Aug 2022. 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-2021-4040 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.activemq:artemis-core-client (Maven): affected all versions; fixed in 2.19.1
- org.apache.activemq:artemis-core-client (Maven): affected all versions; fixed in 2.19.1

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-2021-4040/ (Markdown: https://insights.sbomify.com/CVE-2021-4040/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4040
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4040
- OSV: https://osv.dev/vulnerability/CVE-2021-4040

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4040/
Summaries are generated and may contain mistakes; the official description above is the record.