What is CVE-2021-26355?

CVE-2021-26355 is a medium-severity vulnerability in AMD 3rd Gen Epyc, classified under Protection Mechanism Failure. CVSS score: 5.5/10. Published 2023-01-11.

How severe is CVE-2021-26355?

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

Vulnerability in AMD 3rd Gen Epyc

CVE-2021-26355

Insufficient fencing and checks in System Management Unit (SMU) may result in access to invalid message port registers that could result in a potential denial-of-service.

Published 2023-01-11 · 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: 0.002 (7.0th percentile), scored 2026-11-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure

References

www.amd.com/en/corporate/product-security/bulletin/AMD-SB-1032 (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2021-26355?: CVE-2021-26355 is a medium-severity vulnerability in AMD 3rd Gen Epyc, classified under Protection Mechanism Failure. CVSS score: 5.5/10. Published 2023-01-11.
How severe is CVE-2021-26355?: Medium severity. CVSS v3 base score is 5.5 out of 10.