Mbed TLS in Zephyr firmware: identifiers and CRA notes

What it is

Mbed TLS

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Notes on this component

Mbed TLS, the TLS and cryptography library behind CONFIG_MBEDTLS. Zephyr pins its own copy, which its repository describes as not a mirror of the official one, so the commit in `west.yml` is not an upstream commit and gives no release number. Flaws are published in the Mbed TLS security advisories and as CVEs under arm:mbed_tls and trustedfirmware:mbed_tls; the most serious of the current set are CVE-2026-34877 (a serialized SSL session or context an attacker can modify induces memory corruption and can reach arbitrary code execution; 2.19.0 through 3.6.5 and 4.0.0, fixed in 3.6.6), CVE-2026-34873 (client impersonation while resuming a TLS 1.3 session; 3.5.0 through 4.0.0, fixed in 3.6.6 and 4.1.0) and CVE-2026-34875 (a buffer overflow when exporting a finite-field Diffie-Hellman public key; through 3.6.5, fixed in 3.6.6). The separate `mbedtls-3.6` module is a second copy on its own release schedule and has to be checked on its own.

Also a subsystem, switched on by CONFIG_MBEDTLS. Mbed TLS, pulled in as a Zephyr module, so its vulnerabilities are filed against arm:mbed_tls at the module's own version and not against the Zephyr kernel. CVE family is TLS record and handshake handling, X.509 certificate parsing, and side-channel findings in the crypto primitives. Advisories Mbed TLS published in July 2026 include CVE-2026-50713 (heap corruption, up to remote code execution, when a DTLS peer renegotiates early after a corrupted record, affecting 3.6.3 to 3.6.6), CVE-2026-49300 (an invalid basicConstraints extension makes an end-entity certificate read as a CA, affecting every version up to 3.6.6 and 4.0.0 to 4.1.0, fixed in 3.6.7 and 4.1.1) and CVE-2026-50580 (a malicious TLS 1.2 server makes a client with a long PSK identity write past its output buffer in an ECDHE-PSK handshake, fixed in 3.6.7 and 4.1.1). All three are rated high. The version comes from the mbedtls west module component, because the Zephyr version tells you nothing about which Mbed TLS was vendored.

Where it hides in a firmware SBOM

Zephyr lists a west module by its west name, with no PURL or CPE. Vulnerability feeds cannot find it from that listing alone, which is why the SBOM check adds the identifiers below.

It is compiled into the kernel image when CONFIG_MBEDTLS 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

PURLpackage URL: a standard way to name a software package

pkg:github/Mbed-TLS/mbedtls@{version}

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

cpe:2.3:a:arm:mbed_tls:{version}:*:*:*:*:*:*:*

{version} is filled in from your build. The version is read from the upstream release tag.

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

Honest gaps

Vendor: arm.

Where this row comes from

https://nvd.nist.gov/vuln/detail/CVE-2026-34877
Checked on 10 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 Mbed TLS

• The CRA for ESP-IDF teams: real CPEs out of the box, and the parts they do not cover
• The CRA for Zephyr developers: what the law asks, what west spdx gives you, and what is left
• Firmware SBOMs that actually match CVEs: identifiers, CPE versus purl, and where C libraries hide

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