# CVE-2026-54412: MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

> A remote attacker can crash MQTT-C clients or disclose heap memory via a crafted PUBLISH packet due to integer underflow and out-of-bounds read.

- **Severity:** High 7.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/AU:Y/V:D`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Jun 2026
- **Updated:** 10 Aug 2026
- **Also known as:** GHSA-28cw-rpqc-wqqj

## What is CVE-2026-54412?

CVE-2026-54412 is a high-severity vulnerability in LiamBindle MQTT-C, published on 14 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

LiamBindle MQTT-C through version 1.1.6 contains a heap-based out-of-bounds read and integer underflow in the mqtt_unpack_publish_response function in src/mqtt.c that allows a remote unauthenticated attacker controlling an MQTT broker - or able to inject MQTT traffic into an unencrypted session - to crash a subscribed MQTT-C client and potentially disclose adjacent heap memory by sending a single crafted PUBLISH packet.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-54412?


## How do I fix CVE-2026-54412?

No fix has been published for CVE-2026-54412 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54412 being exploited?

There is no known exploitation of CVE-2026-54412 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54412 and fix it if it is affected.

What it is: CVE-2026-54412 is a high-severity vulnerability in LiamBindle MQTT-C, published on 14 Jun 2026. 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-2026-54412 in the wild and no public exploit code.

Affected product: LiamBindle MQTT-C. 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-2026-54412/ (Markdown: https://insights.sbomify.com/CVE-2026-54412/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54412
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54412
- OSV: https://osv.dev/vulnerability/CVE-2026-54412

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54412/
Summaries are generated and may contain mistakes; the official description above is the record.