What is CVE-2021-36357?

CVE-2021-36357 is a critical-severity vulnerability in Openpowerfoundation Skiboot, classified under Incorrect Conversion between Numeric Types. CVSS score: 9.8/10. Published 2021-10-22.

How severe is CVE-2021-36357?

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

Vulnerability in Openpowerfoundation Skiboot

CVE-2021-36357

An issue was discovered in OpenPOWER 2.6 firmware. unpack_timestamp() calls le32_to_cpu() for endian conversion of a uint16_t "year" value, resulting in a type mismatch that can truncate a higher integer value to a smaller one, and bypass a timestamp check. The fix is to use the right endian conversion function.

Published 2021-10-22 · 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: 0.012 (67.0th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 67th percentile — 67.0% 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

Openpowerfoundation Skiboot — versions 2.6

Weakness classification (CWE)

CWE-681 — Incorrect Conversion between Numeric Types

References

github.com/open-power/skiboot/commit/5be38b672c1410e2f10acd3ad2eecfdc81d5daf7 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-36357?: CVE-2021-36357 is a critical-severity vulnerability in Openpowerfoundation Skiboot, classified under Incorrect Conversion between Numeric Types. CVSS score: 9.8/10. Published 2021-10-22.
How severe is CVE-2021-36357?: Critical severity. CVSS v3 base score is 9.8 out of 10.