view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 3.0.0 to 4.9.0, the preview route derives an example name from the URL and calls it with public_send. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class. As a result, inherited public methods on ViewComponent::Preview are route-reachable. The most important one is render_with_template, which accepts template: and locals:. Those values can come from request params and are later passed to Rails as render template:. If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable. This vulnerability is fixed in 4.9.0.

Affected: RubyGems: view_component

### Summary

The preview route derives an example name from the URL and calls it with `public_send`. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class.

As a result, inherited public methods on `ViewComponent::Preview` are route-reachable. The most important one is `render_with_template`, which accepts `template:` and `locals:`. Those values can come from request params and are later passed to Rails as `render template:`.

If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable.

Severity: High if preview routes are externally reachable; Medium otherwise.

Affected files:

- `lib/view_component/preview.rb` - `app/controllers/concerns/view_component/preview_actions.rb` - `app/views/view_components/preview.html.erb`

### Relevant Code

`app/controllers/concerns/view_component/preview_actions.rb`:

```ruby @example_name = File.basename(params[:path]) @render_args = @preview.render_args(@example_name, params: params.permit!) ```

`lib/view_component/preview.rb`:

```ruby example_params_names = instance_method(example).parameters.map(&:last) provided_params = params.slice(*example_params_names).to_h.symbolize_keys result = provided_params.empty? ? new.public_send(example) : new.public_send(example, **provided_params) ```

`app/views/view_components/preview.html.erb`:

```erb <%= render template: @render_args[:template], locals: @render_args[:locals] || {} %> `…

Affected: Ubuntu:24.04:LTS: ruby-view-component

view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 3.0.0 to 4.9.0, the preview route derives an example name from the URL and calls it with public_send. The code does not verify that the requested method is one of the preview examples explicitly defined by the preview class. As a result, inherited public methods on ViewComponent::Preview are route-reachable. The most important one is render_with_template, which accepts template: and locals:. Those values can come from request params and are later passed to Rails as render template:. If previews are exposed, an attacker can render internal Rails templates that are not otherwise routable. This vulnerability is fixed in 4.9.0.