CVE-2026-84319: Nginx UI: MCP configuration tools bypass restricted directive validation and allow secondary authenticated users to execute NJS in Nginx worker context

The regular HTTP configuration API rejects restricted Nginx directives such as load_module, js_import, and js_content.

However, the MCP configuration interface allows a secondary authenticated user to write and apply equivalent restricted configuration content. In the lab, this allowed the user to load ngx_http_js_module.so, import attacker-controlled JavaScript, reload Nginx, and execute NJS in the Nginx worker context.

This is authenticated and is not OS command execution by itself.