← Vulnerability feed

Vulnerability record · CVE-2026-42221 · published 4 May 2026

CVE-2026-42221: Nginxui nginx ui missing authentication for critical function vulnerability

Nginxui · Nginx Ui

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.

9.8 CVSS 3.1 Critical EPSS 1.6% · top 25.1% CWE-306 · Missing authentication for critical function
9.8CVSS 3.1 base score
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

Track CVE-2026-42221 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.9CVE-2026-44015Nginxui nginx ui server-side request forgery (ssrf) vulnerabilityNginx UI is a web user interface for the Nginx web server. In 2.3.4 and earlier, an authenticated user can perform Server-Side Request Forgery (SSRF)…EPSS 0.39%9.9CVE-2026-33030Nginxui nginx ui os command injection vulnerabilityNginx UI is a web user interface for the Nginx web server. In versions 2.3.3 and prior, Nginx-UI contains an Insecure Direct Object Reference (IDOR) …EPSS 0.38%9.8CVE-2026-42222Nginxui nginx ui improper access control vulnerabilityNginx UI is a web user interface for the Nginx web server. In version 2.3.5, an unauthenticated bootstrap takeover exists in nginx-ui during the init…EPSS 0.47%9.8CVE-2026-33032Nginxui nginx ui missing authentication for critical function vulnerabilityNginx UI is a web user interface for the Nginx web server. In versions 2.3.5 and prior, the nginx-ui MCP (Model Context Protocol) integration exposes…EPSS 2.5%9.8CVE-2026-27944Nginxui nginx ui missing authentication for critical function vulnerabilityNginx UI is a web user interface for the Nginx web server. Prior to version 2.3.3, the /api/backup endpoint is accessible without authentication and …EPSS 1.0%9.8CVE-2024-23827Nginxui nginx ui path traversal vulnerabilityNginx-UI is a web interface to manage Nginx configurations. The Import Certificate feature allows arbitrary write into the system. The feature does n…EPSS 0.70%9.4CVE-2026-33026Nginxui nginx ui cleartext storage of sensitive data vulnerabilityNginx UI is a web user interface for the Nginx web server. Prior to version 2.3.4, the nginx-ui backup restore mechanism allows attackers to tamper w…EPSS 0.21%9.0CVE-2026-42238Nginxui nginx ui code injection vulnerabilityNginx UI is a web user interface for the Nginx web server. Prior to version 2.3.8, nginx-ui exposes a backup restore endpoint (POST /api/restore) tha…EPSS 0.83%

Source: NIST National Vulnerability Database (record CVE-2026-42221), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.