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.

Affected: Go: github.com/0xJacky/Nginx-UI

### Summary 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.

### Details #### Vulnerable Code

**`mcp/router.go:9-17` - Auth asymmetry between endpoints**

```go func InitRouter(r *gin.Engine) { r.Any("/mcp", middleware.IPWhiteList(), middleware.AuthRequired(), func(c *gin.Context) { mcp.ServeHTTP(c) }) r.Any("/mcp_message", middleware.IPWhiteList(), func(c *gin.Context) { mcp.ServeHTTP(c) }) } ```

The `/mcp` endpoint has `middleware.AuthRequired()`, but `/mcp_message` does not. Both endpoints route to the same `mcp.ServeHTTP()` handler, which processes all MCP tool invocations.

**`internal/middleware/ip_whitelist.go:11-26` - Empty whitelist allows all**

```go func IPWhiteList() gin.HandlerFunc { return func(c *gin.Context) { clientIP := c.ClientIP() if len(settings.AuthSettings.IPWhiteList) == 0 || clientIP == "" || clientIP == "127.0.0.1" || clientIP == "::1" { c.Next() return } // ... } } ```

When `IPW…

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in nginx-ui ausnutzen, um sich Administratorrechte zu verschaffen, beliebigen Code auszuführen, Daten zu manipulieren, Sicherheitsmaßnahmen zu umgehen oder einen Denial-of-Service-Zustand herbeizuführen.