Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:L) | Low availability impact |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
About Zimaspace Zimaos
CVE-2026-21891 affects Zimaspace Zimaos, a product from Zimaspace. Before acting, confirm where Zimaspace Zimaos runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: 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.
The weakness class is Improper Authentication. The software does not properly prove who a user is.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Zimaspace Zimaos |
| Affected versions | Zimaos up to and including 1.5.0 |
| Published | Jan 8, 2026 |
| Last modified | Jun 17, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Zimaspace Zimaos and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Zimaspace Zimaos named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Zimaspace Zimaos to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-287: Improper Authentication More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
ZimaOS is a fork of CasaOS, an operating system for Zima devices and x86-64 systems with UEFI. Prior to version 1.5.3, a proxy endpoint (/v1/sys/proxy) exposed by ZimaOS's web interface can be abused (via an externally reachable domain using a Cloudflare Tunnel) to make requests to internal localhost services. This results in unauthenticated access to internal-only endpoints and sensitive local services when the product is reachable from the Internet through a Cloudflare Tunnel. This issue has been patched in version 1.5.3.
ZimaOS is a fork of CasaOS, an operating system for Zima devices and x86-64 systems with UEFI. In version 1.5.2-beta3, the application enforces restrictions in the frontend/UI to prevent users from creating files or folders in internal OS paths. However, when interacting directly with the API, the restrictions are bypass-able. By sending a crafted request targeting paths like /etc, /usr, or other sensitive system directories, the API successfully creates files or directories in locations where normal users should have no write access. This indicates that the API does not properly validate the target path, allowing unauthorized operations on critical system directories. No known patch is publicly available.
Dokans Multi-Tenancy Based eCommerce Platform SaaS 3.9.2 allows unauthenticated remote attackers to obtain sensitive application configuration data via direct request to /script/.env file. The exposed file contains Laravel application encryption key (APP_KEY), database credentials, SMTP/SendGrid API credentials, and internal configuration parameters, enabling complete system compromise including authentication bypass via session token forgery, direct database access to all tenant data, and email infrastructure takeover. Due to the multi-tenancy architecture, this vulnerability affects all tenants in the system.
A remote authentication bypass vulnerability exists in HPE AutoPass License Server (APLS).
The vulnerability exists in BLUVOYIX due to improper authentication in the BLUVOYIX backend APIs. An unauthenticated remote attacker could exploit this vulnerability by sending specially crafted HTTP requests to the vulnerable APIs. Successful exploitation of this vulnerability could allow the attacker to gain full access to customers' data and completely compromise the targeted platform.
Improper authentication in Azure Key Vault allows an unauthorized attacker to elevate privileges over a network.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-21891 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications