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CVE-2026-21891

ZimaOS has Authentication Bypass via System-Level Username

Basic Information

CVE State
PUBLISHED
Reserved Date
January 05, 2026
Published Date
January 08, 2026
Last Updated
January 08, 2026
Vendor
IceWhaleTech
Product
ZimaOS
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.
Tags
nuclei_scanner

CVSS Scores

CVSS v3.1

9.4 - CRITICAL

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

SSVC Information

Exploitation
poc
Automatable
Yes
Technical Impact
total

Exploit Status

Exploited in the Wild
Yes (2026-04-10 00:00:00 UTC) Source

References

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

Known Exploited Vulnerability Information

Source Added Date
The Shadowserver (via CIRCL) 2026-04-10 00:00:00 UTC

Scanner Integrations

Scanner URL Date Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-21891.yaml 2026-06-01 15:34:44 UTC

Timeline

  • CVE ID Reserved

  • CVE Published to Public

  • Added to KEVIntel

  • Detected by Nuclei