MQTT library in Zephyr firmware: identifiers and CRA notes

What it is

MQTT library

• Repository

Notes on this component

Zephyr's MQTT client. CVE family is decoding of broker-supplied packets: remaining-length and topic-length arithmetic, PUBLISH payload bounds. Reachable by whatever the device connects to, and by anyone able to impersonate it when TLS is off. The advisory filed in this family is CVE-2026-15891, where the MQTT-SN client dereferences null while removing a gateway that has stopped responding — rated high and fixed in 4.4.2. Nothing has been filed against the MQTT client itself as of 9 October 2026, so the decoding surface described above is unproven rather than cleared.

Where it hides in a firmware SBOM

It is compiled into the kernel image when CONFIG_MQTT_LIB is y. It does not appear in west spdx output; the only trace is the .config file in your build directory.

The identifiers we assign

CPEthe product name vulnerability databases use to say what a flaw affects

cpe:2.3:o:zephyrproject:zephyr:{version}:*:*:*:*:*:*:*

{version} is filled in from your build. The version is the same as your Zephyr version.

The SBOM check adds these identifiers to a component your build listed without them.

Honest gaps

Vendor: zephyrproject.

This row has no PURL.

Where this row comes from

https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c4g8-4f9p-4746
Checked on 9 October 2026.

Known vulnerabilities

Not checked yet

Vulnerability data changes daily. Check the version you ship in the SBOM check.

CRA notes

• List this component in your SBOM. Annex I, Part II (1): Identify and document components and vulnerabilities, including an SBOMKnow what is in your product. Identify and document its components and their vulnerabilities, including by producing a software bill of materials (SBOM) in a common machine-readable format that covers at least the top-level dependencies.
• Ship the version with no known exploitable vulnerabilities at release. Annex I, Part I (2(a)): Made available without known exploitable vulnerabilitiesWhen you place a release on the market, it must not ship with known vulnerabilities that can be exploited in your product. "Exploitable" means an attacker could effectively use it under practical operating conditions (Article 3(41)), not only in theory or in a lab. The Commission's draft guidance (C(2026) 5252, points 231 to 237; a draft, not binding) gives three ways a vulnerability is "known". One: it is listed in a relevant public vulnerability database, such as the European vulnerability database (EUVD) or another prominent one. Two: you learned of it from information that is not public, for example a security researcher's coordinated disclosure or your own testing and analysis; a vulnerability you know about and have not disclosed still counts. Three: it has been publicly and prominently reported in reliable media, whether specialist security publications or general news. A report is not yet proof: it does not by itself mean the vulnerability can be exploited in practice or applies to your product, so investigate promptly and confirm whether it does. A limited time may pass between the first report and that confirmation. If a vulnerability becomes known shortly before release, you decide from your cybersecurity risk assessment whether the release can go out or the vulnerability must be fixed first. Weigh its severity, exploitability and potential impact, and the risks to the product once in use; you may also weigh the risks of delaying the release, for example because it fixes other exploitable vulnerabilities. After release, the Part II vulnerability handling requirements still apply. Check your components against vulnerability databases before each release, and fix or justify what you find.
• An SBOM without this subsystem under-reports what is in the image. Annex I, Part II (1): Identify and document components and vulnerabilities, including an SBOMKnow what is in your product. Identify and document its components and their vulnerabilities, including by producing a software bill of materials (SBOM) in a common machine-readable format that covers at least the top-level dependencies.

Source: Annex I of Regulation (EU) 2024/2847 (Cyber Resilience Act), legal state 2026.10.13-1.

Related Zephyr components

No related components yet.

Guides that mention MQTT library

• The CRA for Zephyr developers: what the law asks, what west spdx gives you, and what is left

Next step

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