# CVE-2023-33657: Use after free in n/a

> An attacker can cause a denial of service in NanoMQ by triggering a use-after-free vulnerability in the MQTT message handling logic.

- **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:** No
- **Published:** 8 Jun 2023
- **Updated:** 6 Jan 2025
- **Also known as:** GHSA-crqc-c8fj-8qjx

## What is CVE-2023-33657?

CVE-2023-33657 is a high-severity use after free vulnerability in n/a, published on 8 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use-after-free vulnerability exists in NanoMQ 0.17.2. The vulnerability can be triggered by calling the function nni_mqtt_msg_get_publish_property() in the file mqtt_msg.c. This vulnerability is caused by improper data tracing, and an attacker could exploit it to cause a denial of service attack.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2023-33657?

It affects 1 product.


Products: Emqx Nanomq.

## How do I fix CVE-2023-33657?

No fix has been published for CVE-2023-33657 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-33657 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-33657 exists.

## Other vulnerabilities in n/a

- [CVE-2024-42655](https://insights.sbomify.com/CVE-2024-42655/): Missing authorization in n/a (high 8.8)
- [CVE-2025-59947](https://insights.sbomify.com/CVE-2025-59947/): NanoMQ has Buffer Overflow (high 8.5)
- [CVE-2023-34488](https://insights.sbomify.com/CVE-2023-34488/): Memory corruption in n/a (high 8.0)
- [CVE-2026-32135](https://insights.sbomify.com/CVE-2026-32135/): NanoMQ has Heap Buffer Overflow in URI Parameter Parsing (high 7.7)
- [CVE-2026-36590](https://insights.sbomify.com/CVE-2026-36590/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-33657 and fix it if it is affected.

What it is: CVE-2023-33657 is a high-severity use after free vulnerability in n/a, published on 8 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-33657 exists.

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-2023-33657/ (Markdown: https://insights.sbomify.com/CVE-2023-33657/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-33657
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-33657
- OSV: https://osv.dev/vulnerability/CVE-2023-33657

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-33657/
Summaries are generated and may contain mistakes; the official description above is the record.