CVE-2026-21891 (GCVE-0-2026-21891)

Vulnerability from cvelistv5 – Published: 2026-01-08 14:00 – Updated: 2026-01-08 15:55
VLAI Previdian
Title
ZimaOS has Authentication Bypass via System-Level Username
Summary
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.
Severity
9.4 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
SSVC
Exploitation: poc Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-01-08 14:52 UTC
CWE
  • CWE-287 - Improper Authentication
Assigner
References
Impacted products
Vendor Product Version
IceWhaleTech ZimaOS Affected: <= 1.5.0
Create a notification for this product.
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: e5de57ea-cedb-48a3-9aeb-1888804e5034

Vulnerability ID: CVE-2026-21891

Status: Confirmed

Status Updated: 2026-04-10 02:00 CEST

Exploited: Yes

Timestamps
First Seen: 2026-04-10
Asserted: 2026-04-10
Scope
Notes: ZimaOS has Authentication Bypass via System-Level Username | Affected: IceWhale Tech / ZimaOS | CVSS: 9.4 (CRITICAL) | EPSS: 0.0235 | Used in malware: unknown | Not yet in CISA KEV: True
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: previdian

Details
Feed Previdian (previdian.com)
Title ZimaOS has Authentication Bypass via System-Level Username
Cve Id CVE-2026-21891
Vendor IceWhale Tech
Ghsa Id None
Product ZimaOS
Added Date 2026-04-10T00:00:00.000Z
Cvss Score 9.4
Epss Score 0.0235
Previous Ids
Cvss Severity CRITICAL
Virtual Patch False
Cvss Estimated False
Epss Percentile 0.8307
Used In Malware unknown
Vulnerability Id CVE-2026-21891
Ahead Of Cisa Kev None
Not Yet In Cisa Kev True
References
Created: 2026-10-02 09:09 CEST | Updated: 2026-10-02 09:09 CEST
Show details on NVD website
To clipboard 

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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.