What is CVE-2026-21891?

CVE-2026-21891 is a critical-severity vulnerability in Icewhaletech Zimaos, classified under Improper Authentication. CVSS score: 9.4/10. Published 2026-01-08.

How severe is CVE-2026-21891?

Critical severity. CVSS v3 base score is 9.4 out of 10.

Auth bypass in Icewhaletech Zimaos

CVE-2026-21891

ZimaOS is a fork of CasaOS, an operating system for Zima devices and x86-64 systems with UEFI. In versions up to and including 1.5.0, the application checks the validity of the username but appears to skip, misinterpret, or incorrectly val…

Vulnerability class: Broken Authentication

EPSS: 0.114 (93.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.4 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L.

Affected products

Icewhaletech Zimaos — versions <= 1.5.0

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

https://github.com/IceWhaleTech/ZimaOS/security/advisories/GHSA-xj93-qw9p-jxq4 (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-21891?: CVE-2026-21891 is a critical-severity vulnerability in Icewhaletech Zimaos, classified under Improper Authentication. CVSS score: 9.4/10. Published 2026-01-08.
How severe is CVE-2026-21891?: Critical severity. CVSS v3 base score is 9.4 out of 10.