What is CVE-2021-40506?

CVE-2021-40506 is a critical-severity vulnerability in Openrisc Or1200, classified under Improper Authentication. CVSS score: 9.8/10. Published 2023-04-18.

How severe is CVE-2021-40506?

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

Auth bypass in Openrisc Or1200

CVE-2021-40506

An issue was discovered in the ALU unit of the OR1200 (aka OpenRISC 1200) processor 2011-09-10 through 2015-11-11. The overflow flag is not being updated for the msb and mac instructions, which results in an incorrect value in the overflow flag. Any software that relies on this flag may experience corruption in execution.

Vulnerability class: Broken Authentication

Published 2023-04-18 · 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: 0.007 (52.7th percentile), scored 2026-10-07.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 52.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

github.com/openrisc/or1200/commit/2c0765d7ba12813df273cd693a99c4e744f0fbd5 (Patch)
seth.engr.tamu.edu/software-releases/thehuzz/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-40506?: CVE-2021-40506 is a critical-severity vulnerability in Openrisc Or1200, classified under Improper Authentication. CVSS score: 9.8/10. Published 2023-04-18.
How severe is CVE-2021-40506?: Critical severity. CVSS v3 base score is 9.8 out of 10.