GHSA-4w7w-66w2-5vf9

### Summary

Any files ending with `.map` even out side the project can be returned to the browser.

### 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)) - have a sensitive content in files ending with `.map` and the path is predictable

### Details

In Vite v7.3.1, the dev server’s handling of `.map` requests for optimized dependencies resolves file paths and calls `readFile` without restricting `../` segments in the URL. As a result, it is possible to bypass the [`server.fs.strict`](https://vite.dev/config/server-options#server-fs-strict) allow list and retrieve `.map` files located outside the project root, provided they can be parsed as valid source map JSON.

### PoC 1. Create a minimal PoC sourcemap outside the project root ```bash cat > /tmp/poc.map <<'EOF' {"version":3,"file":"x.js","sources":[],"names":[],"mappings":""} EOF ``` 2. Start the Vite dev server (example) ```bash pnpm -C playground/fs-serve dev --host 127.0.0.1 --port 18080 ``` 3. Confirm that direct `/@fs` access is blocked by `strict` (returns 403) <img width="4004" height="1038" alt="image" src="https://github.com/user-attachments/assets/15a859a8-1dc6-4105-8d58-80527c0dd9ab" /> 4. Inject `../` segments under the optimized deps `.map` URL prefix to reach `/tmp/poc.map` <img width="2790" height="846" alt="image" src="https://github.com/user-attachments/assets/5d02957d-2e6a-4c45-9819-3f024e0e81f2" />