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CVE-2026-21891— ZimaOS has Authentication Bypass via System-Level Username

Quick assessment

Affected
IceWhaleTech ZimaOS
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

ZimaOS是IceWhaleTech的一个开源的操作系统项目，旨在提供一个轻量级、高性能、安全的操作系统环境。 ZimaOS 1.5.0及之前版本存在安全漏洞，该漏洞源于密码验证不当，可能导致未经授权的访问。

CVSS 9.4 · Critical EPSS 2.35% · P83

Public Exploits 1

Nuclei · 1 CVE-2026-21891.yaml [template]

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts
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I. Basic Information for CVE-2026-21891

Vulnerability Information
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Vulnerability Title
ZimaOS has Authentication Bypass via System-Level Username
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
ZimaOS 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ZimaOS是IceWhaleTech的一个开源的操作系统项目，旨在提供一个轻量级、高性能、安全的操作系统环境。 ZimaOS 1.5.0及之前版本存在安全漏洞，该漏洞源于密码验证不当，可能导致未经授权的访问。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
IceWhaleTech ZimaOS <= 1.5.0 -

II. Public POCs for CVE-2026-21891

# POC Description Source Link Shenlong Link
1 ZimaOS <= 1.5.0 contains a broken authentication caused by improper password validation for known system service accounts in the login function, letting attackers authenticate with any password for these accounts, exploit requires knowledge of common usernames. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-21891.yaml POC Details
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III. Intelligence Information for CVE-2026-21891

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IV. Related Vulnerabilities

Same product: ZimaOS
Same vendor: IceWhaleTech
Same weakness: CWE-287

V. Comments for CVE-2026-21891

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