Summary

The contents of arbitrary files can be returned to the browser if the dev server is running on Node or Bun.

Impact

Only apps with the following conditions are affected.

• explicitly exposing the Vite dev server to the network (using --host or server.host config option)
• running the Vite dev server on runtimes that are not Deno (e.g. Node, Bun)

Details

HTTP 1.1 spec (RFC 9112) does not allow # in request-target. Although an attacker can send such a request. For those requests with an invalid request-line (it includes request-target), the spec recommends to reject them with 400 or 301. The same can be said for HTTP 2 (ref1, ref2, ref3).

On Node and Bun, those requests are not rejected internally and is passed to the user land. For those requests, the value of http.IncomingMessage.url contains #. Vite assumed req.url won't contain # when checking server.fs.deny, allowing those kinds of requests to bypass the check.

On Deno, those requests are not rejected internally and is passed to the user land as well. But for those requests, the value of http.IncomingMessage.url did not contain #.

PoC

npm create vite@latest
cd vite-project/
npm install
npm run dev

send request to read /etc/passwd

curl --request-target /@fs/Users/doggy/Desktop/vite-project/#/../../../../../etc/passwd http://127.0.0.1:5173