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Trusted Firmware MOperating system · Trustedfirmware

CVE-2021-40327

MEDIUM · 5.9 CVSS v3.1 Published 2022-01-13
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Trusted Firmware-M (TF-M) 1.4.0, when Profile Small is used, has incorrect access control. NSPE can access a secure key (held by the Crypto service) based solely on knowledge of its key ID. For example, there is no authorization check associated with the relationship between a caller and a key owner.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-862

The application checks who you are but not whether you're allowed to perform a given action, so any authenticated user can reach things meant for others. This is the classic “change the ID in the URL” bug. The fix is an authorization check on every request, evaluated against the acting user's permissions.

General guidance for the missing authorization class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Trusted Firmware MOperating system
Affected:= 1.4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch git.trustedfirmware.org →
Recommended fix Moderate confidence

TF-M 1.5.0 or later stable release

  1. 1. Navigate to the Trusted Firmware M official repository at https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/
  2. 2. Identify the current HEAD of the main branch or stable release branch
  3. 3. Obtain TF-M version 1.5.0 or later (the first release after 1.4.0 that addresses this authorization bypass)
  4. 4. Update the TF-M dependency in your project to point to the fixed version
  5. 5. Rebuild the firmware with the new TF-M version
  6. 6. Re-flash the updated firmware to all affected devices
  7. 7. Verify that the Crypto service now properly performs authorization checks before allowing key access from NSPE
Caveat Review TF-M 1.5.0 release notes for any API changes or migration requirements from version 1.4.0, particularly around Crypto service configuration and key management

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-40327 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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