CVE-2026-42221

HIGH 8.1

nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim

CVSS Score

8.1

EPSS Score

0.0%

EPSS Percentile

0th

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	CWE-306
Vendor	0xjacky
Product	nginx-ui
Published	May 4, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Affected Versions

0xJacky / nginx-ui

>= 2.0.0, < 2.3.8

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp github.com: https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8