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CVE-2026-21891

9.4 · CRITICAL

ZimaOS is a fork of CasaOS, an operating system for Zima devices and x86-64 systems with UEFI.

Published Jan 8, 2026CWE-287EPSS 2.32%

Overview

CVE-2026-21891 is a critical-severity vulnerability. It was published on January 8, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/IceWhaleTech/ZimaOS/security/advisories/GHSA-xj93-qw9p-jxq4GitHubgithub.com/IceWhaleTech/ZimaOS/security/advisories/GHSA-xj93-qw9p-jxq4

How CyberStrike helps

Frequently asked questions

What is CVE-2026-21891?

CVE-2026-21891 is a critical-severity vulnerability. It was published on January 8, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

How severe is CVE-2026-21891?

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-21891?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-21891?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-21891 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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