CVE-2026-44836

viewcomponent 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 publicsend. 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 renderwithtemplate, 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.