Nginx 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 two HTTP endpoints: /mcp and /mcp_message. While /mcp requires both IP whitelisting and authentication (AuthRequired() middleware), the /mcp_message endpoint only applies IP whitelisting - and the default IP whitelist is empty, which the middleware treats as "allow all". This means any network attacker can invoke all MCP tools without authentication, including restarting nginx, creating/modifying/deleting nginx configuration files, and triggering automatic config reloads - achieving complete nginx service takeover. At time of publication, there are no publicly available patches.
PoC: CVE-2026-33032
One missing function call on the route registration was enough to turn the MCP interface into an unauthenticated RCE gateway.
PoC: CVE-2026-33032-nginx-ui-vuln-lab
Docker Compose setup to demonstrate the nginx-ui missing authentication vulnerability
PoC: cve-2026-33032-scanner
Non-destructive vulnerability scanner for Nginx-UI MCP Endpoint Authentication Bypass (CVE-2026-33032)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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