Summary

server.fs 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) - 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" />

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) - 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 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" />

Summary

The contents of files that are specified by server.fs.deny 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) - the sensitive file exists in the allowed directories specified by server.fs.allow - the sensitive file is denied with a pattern that matches a file by server.fs.deny

Details

On the Vite dev server, files that should be blocked by server.fs.deny (e.g., .env, .crt) can be retrieved with HTTP 200 responses when query parameters such as ?raw, ?import&raw, or ?import&url&inline are appended.

PoC

1. Start the dev server: pnpm exec vite root --host 127.0.0.1 --port 5175 --strictPort 2. Confirm that server.fs.deny is enforced (expect 403): curl -i http://127.0.0.1:5175/src/.env | head -n 20 <img width="3944" height="1092" alt="image" src="https://github.com/user-attachments/assets/ecb9f2e0-e08f-4ac7-b194-e0f988c4cd4f" /> 3. Confirm that the same files can be retrieved with query parameters (expect 200): <img width="2014" height="373" alt="image" src="https://github.com/user-attachments/assets/76bc2a6a-44f4-4161-ae47-eab5ae0c04a8" />