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…

PriorityP267critical9.8CVSS 3.1

AVNACLPRNUINSUCHIHAH

EPSS

0.35%

26.4th percentile

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.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
0xjacky	nginx-ui	—	—
github.com	0xjacky_nginx-ui	>= 2.0.0 < 2.3.8	2.3.8
nginxui	nginx_ui	>= 2.0.0 < 2.3.8	2.3.8

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