CVE-2026-21891

9.4 CRITICAL 2% exploit odds Fix listed Auth & access OS & kernel

What it is

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 validate the password when the provided username matches a known system service account. The application's login function fails to properly handle the password validation result for these users, effectively granting authenticated access to anyone who knows one of these common usernames and provides any password. As of time of publication, no known patched versions are available.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering.
Exploit odds: 2.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-01-08 14:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:19 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 2.3% in the next 30 days (EPSS).
Severity: 9.4 CRITICAL (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-01-08 14:15 UTC
Last modified: 2026-06-17 10:19 UTC
Exploit probability: 2.3% · EPSS, next 30 days
Weakness: CWE-287 · Improper authentication
Record status: Analyzed

Affected

Zimaspace Zimaos ≤ 1.5.0

Attack profile CVSS 3.1 · 9.4

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: Low

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Is it in your code?

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Fix and advisories

References

NVD record · CVE.org record