Nordic Secure Immutable Bootloader (NSIB / b0) in Zephyr firmware: identifiers and CRA notes

What it is

Nordic Secure Immutable Bootloader (NSIB / b0)

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Notes on this component

Nordic's own immutable first-stage bootloader (`b0`, source at `subsys/bootloader` in `sdk-nrf`), enabled by `CONFIG_SECURE_BOOT=y`. It is NOT MCUboot: NSIB is immutable (burned once, never updated) and its only job is verifying and chainloading the next stage, which is commonly MCUboot itself when `CONFIG_BOOTLOADER_MCUBOOT=y` is ALSO set — in that configuration MCUboot becomes the upgradable second-stage bootloader NSIB starts (see the `ncs-mcuboot` and plain `mcuboot` rows' notes, which say the same from the other side). Like any bootloader, it is a separate build and its own image, not in the application's SBOM; ask for its SBOM separately. No CPE exists for it; Nordic publishes no public CVE feed naming NSIB independently of general nRF Connect SDK release notes.

Where it hides in a firmware SBOM

It is compiled into the kernel image when CONFIG_SECURE_BOOT 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

No PURL and no CPE are recorded for this row.

{version} is filled in from your build. The version is read from the version your SBOM already carries for it.

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

Honest gaps

Vendor: nordicsemiconductor.

This row has no CPE and no PURL, so feeds cannot be matched by identifier.

Where this row comes from

https://github.com/nrfconnect/sdk-nrf/blob/v3.4.1/sysbuild/Kconfig.secureboot#L7
Checked on 7 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.
• A bootloader is part of how you deliver updates, so its update path matters here. Annex I, Part I (2(c)): Vulnerabilities can be fixed through security updatesVulnerabilities must be fixable through security updates. Where applicable, that includes automatic security updates that are switched on by default and install within an appropriate time, with a clear and easy-to-use way to opt out, together with telling users when an update is available and letting them postpone it for a while.

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 Nordic Secure Immutable Bootloader (NSIB / b0)

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

Next step

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