Nuxt is an open-source web development framework for Vue.js. From 3.4.0 until 3.21.10 and 4.5.1, an attacker can inject a template key through /__nuxt_island/ props into a dynamic component when `vue.runtimeCompiler: true` is enabled, causing template execution in the Nitro process. This issue is fixed in 3.21.10 and 4.5.1.

Affected: npm: nuxt

## Impact

Nuxt server islands accept props via the `/__nuxt_island/` endpoint. When `vue.runtimeCompiler: true` is enabled (off by default) and the application has a server island component that forwards props into Vue's dynamic component resolution (`<component :is>`, `resolveDynamicComponent`, or `h()`), an attacker can inject a `template` key into the island props to achieve server-side remote code execution in the Nitro process.

```json { "as": { "template": "<attacker-controlled>" } } ```

Vue's runtime template compiler compiles and executes the attacker-controlled `template` in the server process. The same primitive also works on the client side when the runtime compiler is active there, though the server-side path is the primary concern.

Some component libraries expose a polymorphic `as` / `asChild` prop that forwards its value into `<component :is>`; `@nuxt/ui` (via `reka-ui`) is a widely used example. An application is affected if such a component receives the attacker-controlled value, provided `vue.runtimeCompiler` is also enabled. Note this does not require the island author to explicitly forward a prop: island props that the island component does not declare fall through as attributes onto its single root element (standard Vue attribute inheritance), so an island whose root is a polymorphic component receives the attacker's `as` value implicitly. These libraries are not themselves vulnerable; they are noted only because they commonly provide the dynamic-comp…