CVE-2026-42221

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.

• CWE-306

• https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8Release Notes
• https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fpExploit, Mitigation, Vendor Advisory
• https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fpExploit, Mitigation, Vendor Advisory

Published

May 4, 2026

Last Modified

Jun 17, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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