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CVE-2026-42221— nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim

CVSS 8.1 · High EPSS 0.10% · P26
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I. Basic Information for CVE-2026-42221

Vulnerability Information
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Vulnerability Title
nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
关键功能的认证机制缺失
Source: NVD (National Vulnerability Database)
Vulnerability Title
Nginx UI 访问控制错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Nginx UI是Jacky个人开发者的一个 Nginx 的 WebUI。 Nginx UI 2.0.0版本至2.3.8之前版本存在访问控制错误漏洞，该漏洞源于首次运行设置期间公共/api/install端点无需认证，可能导致未认证网络攻击者声明初始管理员账户。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
0xJackynginx-ui >= 2.0.0, < 2.3.8 -

II. Public POCs for CVE-2026-42221

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III. Intelligence Information for CVE-2026-42221

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Same Patch Batch · 0xJacky · 2026-05-04 · 5 CVEs total

CVE-2026-422228.1 HIGHnginx-ui: Unauthenticated first-boot instance claim via POST /api/install allows remote bo
CVE-2026-422206.5 MEDIUMnginx-ui: Authenticated settings disclosure exposes node.secret and enables trusted-node a
CVE-2026-422236.5 MEDIUMnginx-ui: Settings API Exposes Protected Secrets
CVE-2026-42238Unauthenticated Remote Code Execution via Backup Restore in nginx-ui

IV. Related Vulnerabilities

Same product: nginx-ui
Same vendor: 0xJacky
Same weakness: CWE-306

V. Comments for CVE-2026-42221

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