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CVE-2026-21891

Zimaspace Zimaos authentication bypass

9.4 CRITICALPublic exploitEPSS 2.32%
  1. Published8 Jan 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Affected products

Zimaspace Zimaos≤ 1.5.0

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-21891 being actively exploited?

CVE-2026-21891 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 2.32%.

How severe is CVE-2026-21891?

CVE-2026-21891 has a CVSS 3.1 base score of 9.4, rated critical. EPSS estimates a 2.32% probability of exploitation.

Which products are affected by CVE-2026-21891?

Affected products include Zimaspace Zimaos.

How do I fix CVE-2026-21891?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-21891 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.