# CVE-2021-45939: Memory corruption in n/a

> A heap-based buffer overflow in wolfMQTT allows attackers to execute arbitrary code or cause denial of service via crafted packets.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 31 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-jc37-rmrx-qcxg

## What is CVE-2021-45939?

CVE-2021-45939 is a medium-severity memory corruption vulnerability in n/a, published on 31 Dec 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient_DecodePacket (called from MqttClient_WaitType and MqttClient_Subscribe).

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-45939?

It affects 1 product.


Products: Wolfssl Wolfmqtt.

## How do I fix CVE-2021-45939?

No fix has been published for CVE-2021-45939 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-45939 being exploited?

There is no known exploitation of CVE-2021-45939 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-45932](https://insights.sbomify.com/CVE-2021-45932/): Memory corruption in n/a (medium 5.5)
- [CVE-2021-45933](https://insights.sbomify.com/CVE-2021-45933/): Memory corruption in n/a (medium 5.5)
- [CVE-2021-45934](https://insights.sbomify.com/CVE-2021-45934/): Memory corruption in n/a (medium 5.5)
- [CVE-2021-45936](https://insights.sbomify.com/CVE-2021-45936/): Memory corruption in n/a (medium 5.5)
- [CVE-2021-45937](https://insights.sbomify.com/CVE-2021-45937/): Memory corruption in n/a (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-45939 and fix it if it is affected.

What it is: CVE-2021-45939 is a medium-severity memory corruption vulnerability in n/a, published on 31 Dec 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-45939 in the wild and no public exploit code.

Affected product: n/a. 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-2021-45939/ (Markdown: https://insights.sbomify.com/CVE-2021-45939/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-45939
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-45939
- OSV: https://osv.dev/vulnerability/CVE-2021-45939

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-45939/
Summaries are generated and may contain mistakes; the official description above is the record.