Platform
other
Component
zimaos
Fixed in
1.5.1
CVE-2026-21891 describes an authentication bypass vulnerability affecting ZimaOS, a fork of CasaOS. This flaw allows attackers to gain unauthorized access by exploiting a weakness in the password validation process for specific system service accounts. The vulnerability impacts ZimaOS versions up to and including 1.5.0. A patch is available in version 1.5.1.
This authentication bypass vulnerability poses a significant security risk. An attacker who knows a valid system service username can bypass the password check entirely, effectively gaining full access to the ZimaOS system. This could lead to complete system compromise, including data exfiltration, malware installation, and lateral movement within the network. Given ZimaOS's purpose as an operating system for Zima devices and x86-64 systems, the potential impact extends to sensitive data and control over connected hardware. The ease of exploitation, requiring only a known username and any password, amplifies the risk.
CVE-2026-21891 was publicly disclosed on 2026-01-08. As of this writing, there are no publicly available proof-of-concept exploits. The vulnerability's severity is classified as CRITICAL due to the ease of exploitation and the potential for complete system compromise. It is not currently listed on the CISA KEV catalog. Active campaigns are not yet confirmed, but the simplicity of the exploit makes it a likely target for opportunistic attackers.
Exploit Status
EPSS
14.13% (94% percentile)
CISA SSVC
CVSS Vector
Exploitation detected
NextGuard recorded active exploitation indicators in public threat intel feeds.
The primary mitigation for CVE-2026-21891 is to immediately upgrade ZimaOS to version 1.5.1 or later. If upgrading is not immediately feasible due to compatibility issues or system downtime concerns, consider temporarily restricting access to the ZimaOS interface using a firewall or network segmentation. While not a complete solution, this can limit the potential attack surface. Review and audit user accounts, particularly those with system service privileges, to ensure adherence to the principle of least privilege. There are no specific WAF rules or detection signatures readily available for this vulnerability, emphasizing the importance of patching.
Actualizar a una versión parcheada de ZimaOS cuando esté disponible. Como no hay versiones parcheadas disponibles al momento, se recomienda monitorear las actualizaciones de seguridad de IceWhaleTech y aplicar el parche tan pronto como se publique. Mientras tanto, se recomienda deshabilitar o restringir el acceso a las cuentas de servicio del sistema.
Vulnerability analysis and critical alerts directly to your inbox.
CVE-2026-21891 is a critical vulnerability in ZimaOS versions up to 1.5.0 that allows attackers to bypass authentication by using known system service usernames with any password, granting unauthorized access.
If you are running ZimaOS version 1.5.0 or earlier, you are affected by this vulnerability. Check your version and upgrade immediately.
Upgrade ZimaOS to version 1.5.1 or later to remediate the vulnerability. If immediate upgrade is not possible, restrict access using a firewall or network segmentation.
While no active campaigns have been confirmed, the vulnerability's simplicity makes it a likely target for opportunistic attackers. Monitor your systems closely.
Refer to the official ZimaOS security advisory for detailed information and updates regarding CVE-2026-21891: [https://zimaos.com/security/advisories/CVE-2026-21891]
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