CVE-2026-84316: Nginx UI: nginx config directive denylist (ValidateConfigFile) is bypassable via same-line ";" separation → authenticated directive injection (RCE on the official image)

config.ValidateConfigFile is the security control that blocks dangerous nginx directives (js_*, perl_*, load_module of njs/perl modules, user root). Its directive scanner is bypassable: it splits the config by newlines and inspects only the FIRST token of each line, but nginx separates directives with ;, not newlines. Putting a benign directive first and the blocked directive after a ; on the SAME line defeats every check. The include directive is also not on the denylist. As a result, an authenticated caller can inject the exact directives the hardening was meant to block, through EVERY path that calls the validator — POST /api/configs (add), the REST config modify endpoint (api/config/modify.go), the MCP nginx_config_modify tool, and the site/stream save paths (internal/site/save.go, internal/stream/save.go). On deployments where nginx has the njs/perl module (the official uozi/nginx-ui Docker image ships ngx_http_js_module.so), this leads to code execution in the nginx worker; with user root the workers run as root.

This is distinct from the config_add gap (the MCP nginx_config_add tool not calling the validator at all): here the validator IS called and still bypassed, so fixing config_add does not fix this.