CVE-2026-21891
CVSS v3
9.8
CRITICAL
EPSS Score
2.4 %
exploit probability, as of 2026-10-03
CISA KEV
No
known exploited
Exploitation
—
SSVC status
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.
Technical details
- Published
- 2026-01-08
Frequently asked questions
What is 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 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.
Is CVE-2026-21891 actively exploited?
Active exploitation of CVE-2026-21891 has not been confirmed. Its EPSS score was 2.4% on 2026-10-03, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2026-21891?
CVE-2026-21891 has a CVSS v3 base score of 9.8 (CRITICAL severity).
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