Vite Vulnerable to Arbitrary File Read via Vite Dev Server WebSocket

Open Source Vulnerabilities GHSA-p9ff-h696-f583

### Summary [`server.fs`](https://vite.dev/config/server-options#server-fs-strict) check was not enforced to the `fetchModule` method that is exposed in Vite dev server's WebSocket. ### Impact Only apps that match the following conditions are affected: - explicitly exposes the Vite dev server to the network (using `--host` or [`server.host` config option](https://vitejs.dev/config/server-options.html#server-host)) - WebSocket is not disabled by `server.ws: false` Arbitrary files on the server (development machine, CI environment, container, etc.) can be exposed. ### Details If it is possible to connect to the Vite dev server’s WebSocket **without an `Origin` header**, an attacker can invoke `fetchModule` via the custom WebSocket event `vite:invoke` and combine `file://...` with `?raw` (or `?inline`) to retrieve the contents of arbitrary files on the server as a JavaScript string (e.g., `export default "..."`). The access control enforced in the HTTP request path (such as `server.fs.allow`) is not applied to this WebSocket-based execution path. ### PoC 1. Start the dev server on the target Example (used during validation with this repository): ```bash pnpm -C playground/alias exec vite --host 0.0.0.0 --port 5173 ``` 2. Confirm that access is blocked via the HTTP path (example: arbitrary file) ```bash curl -i 'http://localhost:5173/@fs/etc/passwd?raw' ``` Result: `403 Restricted` (outside the allow list) <img width="3898" height="1014" alt="image" src="https://github.com/user-attachments/assets/f6593377-549c-45d7-b562-5c19833438af" /> 3. Confirm that the same file can be retrieved via the WebSocket path By connecting to the HMR WebSocket without an `Origin` header and sending a `vite:invoke` request that calls `fetchModule` with a `file://...` URL and `?raw`, the file contents are returned as a JavaScript module. <img width="1049" height="296" alt="image" src="https://github.com/user-attachments/assets/af969f7b-d34e-4af4-8adb-5e2b83b31972" /> <img width="1382" height="955" alt="image" src="https://github.com/user-attachments/assets/6a230d2e-197a-4c9c-b373-d0129756d5d7" />

Open Source Vulnerabilities CVE-2026-39363

Vite is a frontend tooling framework for JavaScript. From 6.0.0 to before 6.4.2, 7.3.2, and 8.0.5, if it is possible to connect to the Vite dev server’s WebSocket without an Origin header, an attacker can invoke fetchModule via the custom WebSocket event vite:invoke and combine file://... with ?raw (or ?inline) to retrieve the contents of arbitrary files on the server as a JavaScript string (e.g., export default "..."). The access control enforced in the HTTP request path (such as server.fs.allow) is not applied to this WebSocket-based execution path. This vulnerability is fixed in 6.4.2, 7.3.2, and 8.0.5.