CVE-2026-42221 — nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
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 ac…
Published: 2026-05-04 · CVSS: 8.1 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7