What is CVE-2021-27562?

CVE-2021-27562 is a medium-severity vulnerability in Trustedfirmware Trusted Firmware-M, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2021-05-25.

How severe is CVE-2021-27562?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Is CVE-2021-27562 known to be exploited?

Yes. CVE-2021-27562 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 4 public proof-of-concept repositories are indexed.

Buffer overflow in Trustedfirmware Trusted Firmware-M

CVE-2021-27562

In Arm Trusted Firmware M through 1.2, the NS world may trigger a system halt, an overwrite of secure data, or the printing out of secure data when calling secure functions under the NSPE handler mode.

Vulnerability class: Buffer Overflow

Published 2021-05-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.031 (87.5th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 87.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.031 · newest: 0.031 · change: 0.000

Affected products

Trustedfirmware Trusted Firmware-M

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2021-11-03. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2021-11-17.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

developer.arm.com/support/arm-security-updates (Vendor Advisory)
git.trustedfirmware.org/TF-M/trusted-firmware-m.git/tree/docs/security/security… (Permissions Required, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2021-27562?: CVE-2021-27562 is a medium-severity vulnerability in Trustedfirmware Trusted Firmware-M, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2021-05-25.
How severe is CVE-2021-27562?: Medium severity. CVSS v3 base score is 5.5 out of 10.
Is CVE-2021-27562 known to be exploited?: Yes. CVE-2021-27562 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 4 public proof-of-concept repositories are indexed.