What is CVE-2021-40327?

CVE-2021-40327 is a medium-severity vulnerability in Trustedfirmware Trusted Firmware-M, classified under Missing Authorization. CVSS score: 5.9/10. Published 2022-01-13.

How severe is CVE-2021-40327?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Auth bypass in Trustedfirmware Trusted Firmware-M

CVE-2021-40327

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.

Vulnerability class: Broken Access Control

Published 2022-01-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.012 (67.8th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 67.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Trustedfirmware Trusted Firmware-M — versions 1.4.0

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

developer.arm.com/support/arm-security-updates (Third Party Advisory)
git.trustedfirmware.org/TF-M/trusted-firmware-m.git/ (Patch, Vendor Advisory)
tf-m-user-guide.trustedfirmware.org/docs/security/security_advisories/profile_s… (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-40327?: CVE-2021-40327 is a medium-severity vulnerability in Trustedfirmware Trusted Firmware-M, classified under Missing Authorization. CVSS score: 5.9/10. Published 2022-01-13.
How severe is CVE-2021-40327?: Medium severity. CVSS v3 base score is 5.9 out of 10.