CVE-2026-42221

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

Published May 4, 2026 CVSS 3.1 · 8.1 High EPSS 1.3% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-h27v-ph7w-m9fp Nginx-UI: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
History
Type Values Removed Values Added
First Time appeared Nginxui
Nginxui nginx Ui
CPEs cpe:2.3:a:nginxui:nginx_ui:*:*:*:*:*:*:*:*
Vendors & Products Nginxui
Nginxui nginx Ui
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared 0xjacky
0xjacky nginx-ui
Vendors & Products 0xjacky
0xjacky nginx-ui
Type Values Removed Values Added
Description 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.
Title nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
Weaknesses CWE-306
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 5, 2026, 2:14 PM
Reserved
Apr 25, 2026, 5:04 AM
Status
Analyzed
Published
May 4, 2026, 9:16 PM
Modified
Oct 26, 2026, 7:10 PM