CVE-2026-42221
8.1 · HIGHOverview
CVE-2026-42221 is a high-severity vulnerability affecting nginxui nginx_ui. It was published on May 4, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
Nginx UI is a web user interface for the Nginx web server. From version 2.0.0 to before version 2.3.8, an unauthenticated network attacker can claim the initial administrator account on a fresh nginx-ui instance during the first-run setup window. The public /api/install endpoint is reachable without authentication, and the request-encryption flow only protects payload confidentiality in transit; it does not authenticate who is allowed to perform installation. A remote attacker who reaches the service before the legitimate operator can set the admin email, username, and password, causing permanent initial-instance takeover. This issue has been patched in version 2.3.8.
Remediation
Check the references section for vendor advisories and patches from nginxui. Update nginx_ui to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| nginxui | nginx_ui | >= 2.0.0, < 2.3.8 | Affected |
Frequently Asked Questions
What is CVE-2026-42221?
CVE-2026-42221 is a high-severity vulnerability affecting nginxui nginx_ui. It was published on May 4, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).
How severe is CVE-2026-42221?
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-42221?
Check the references section for vendor advisories and patches from nginxui. Update nginx_ui to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-42221?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-42221 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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