Nginx-UI is a web interface to manage Nginx configurations. It is vulnerable to arbitrary command execution by abusing the configuration settings. The `Home > Preference` page exposes a list of system settings such as `Run Mode`, `Jwt Secret`, `Node Secret` and `Terminal Start Command`. While the UI doesn't allow users to modify the `Terminal Start Command` setting, it is possible to do so by sending a request to the API. This issue may lead to authenticated remote code execution, privilege escalation, and information disclosure. This vulnerability has been patched in version 2.0.0.beta.9.

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

### Summary Nginx-UI is a web interface to manage Nginx configurations. It is vulnerable to arbitrary command execution by abusing the configuration settings.

### Details The `Home > Preference` page exposes a list of system settings such as `Run Mode`, `Jwt Secret`, `Node Secret` and `Terminal Start Command`. The latter is used to specify the command to be executed when a user opens a terminal from the web interface. While the UI doesn't allow users to modify the `Terminal Start Command` setting, it is possible to do so by sending a request to the [API](https://github.com/0xJacky/nginx-ui/blob/04bf8ec487f06ab17a9fb7f34a28766e5f53885e/api/system/router.go#L13).

```go func InitPrivateRouter(r *gin.RouterGroup) { r.GET("settings", GetSettings) r.POST("settings", SaveSettings) ... } ```

The [`SaveSettings`](https://github.com/0xJacky/nginx-ui/blob/04bf8ec487f06ab17a9fb7f34a28766e5f53885e/api/system/settings.go#L18) function is used to save the settings. It is protected by the [`authRequired`](https://github.com/0xJacky/nginx-ui/blob/04bf8ec487f06ab17a9fb7f34a28766e5f53885e/router/middleware.go#L45) middleware, which requires a valid JWT token or a `X-Node-Secret` which must equal the `Node Secret` configuration value. However, given the lack of authorization roles, any authenticated user can modify the settings.

The `SaveSettings` function is defined as follows:

```go func SaveSettings(c *gin.Context) { var json struct { Server settings.Server `json…