What is CVE-2021-36226?

CVE-2021-36226 is a critical-severity vulnerability in Westerndigital My Cloud OS, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.8/10. Published 2023-02-06.

How severe is CVE-2021-36226?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Westerndigital My Cloud OS

CVE-2021-36226

Western Digital My Cloud devices before OS5 do not use cryptographically signed Firmware upgrade files.

Published 2023-02-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (55.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 55.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

krebsonsecurity.com/2021/07/another-0-day-looms-for-many-western-digital-users/ (Exploit, Patch, Third Party Advisory)
www.youtube.com/watch (Exploit, Patch, Third Party Advisory)
github.com/pedrib/PoC/blob/master/advisories/Pwn2Own/Tokyo_2020/weekend_destroy… (Exploit, Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-36226?: CVE-2021-36226 is a critical-severity vulnerability in Westerndigital My Cloud OS, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.8/10. Published 2023-02-06.
How severe is CVE-2021-36226?: Critical severity. CVSS v3 base score is 9.8 out of 10.