CVE-2026-42221
Nginx-UI: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
Impact
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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/0xJacky/Nginx-UI | >= 2.0.0, <= 2.3.5 | 2.3.8 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nginxui | Nginx Ui | from 2.0.0 before 2.3.8 |