Nuxt is an open-source web development framework for Vue.js. Prior to 3.19.0 and 4.1.0, A client-side path traversal vulnerability in Nuxt's Island payload revival mechanism allowed attackers to manipulate client-side requests to different endpoints within the same application domain when specific prerendering conditions are met. The vulnerability occurs in the client-side payload revival process (revive-payload.client.ts) where Nuxt Islands are automatically fetched when encountering serialized __nuxt_island objects. During prerendering, if an API endpoint returns user-controlled data containing a crafted __nuxt_island object, he data gets serialized with devalue.stringify and stored in the prerendered page. When a client navigates to the prerendered page, devalue.parse deserializes the payload. The Island reviver attempts to fetch /__nuxt_island/${key}.json where key could contain path traversal sequences. Update to Nuxt 3.19.0+ or 4.1.0+.

Affected: npm: nuxt

### Summary

A client-side path traversal vulnerability in Nuxt's Island payload revival mechanism allowed attackers to manipulate client-side requests to different endpoints within the same application domain when specific prerendering conditions are met.

### Technical Details

The vulnerability occurs in the client-side payload revival process (revive-payload.client.ts) where Nuxt Islands are automatically fetched when encountering serialized `__nuxt_island` objects. The issue affects the following flow:

1. During prerendering, if an API endpoint returns user-controlled data containing a crafted `__nuxt_island` object 2. This data gets serialized with `devalue.stringify` and stored in the prerendered page 3. When a client navigates to the prerendered page, `devalue.parse` deserializes the payload 4. The Island reviver attempts to fetch `/__nuxt_island/${key}.json` where `key` could contain path traversal sequences

### Prerequisites for Exploitation

This vulnerability requires **all** of the following conditions:

1. **Prerendered pages**: The application must use Nuxt's prerendering feature (`nitro.prerender`) 2. **Attacker-controlled API responses**: The attacker must be able to control the response content of an API endpoint that is called during prerendering via `useFetch`, `useAsyncData`, or similar composables 3. **Client-side navigation**: A user must navigate to the prerendered page (not during initial SSR hydration)

### Attack Scenario

```javascript // Malici…