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

Source

https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-21891.yaml

Associated Vulnerability

Title:ZimaOS has Authentication Bypass via System-Level Username (CVE-2026-21891)
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.

Description

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.

File Snapshot

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