Vite's server.fs.deny bypassed with /. for files under project root

Summary

The contents of files in the project root that are denied by a file matching pattern can be returned to the browser.

Impact

Only apps explicitly exposing the Vite dev server to the network (using --host or server.host config option) are affected.
Only files that are under project root and are denied by a file matching pattern can be bypassed.

• Examples of file matching patterns: .env, .env.*, *.{crt,pem}, **/.env
• Examples of other patterns: **/.git/**, .git/**, .git/**/*

Details

server.fs.deny can contain patterns matching against files (by default it includes .env, .env.*, *.{crt,pem} as such patterns).
These patterns were able to bypass for files under root by using a combination of slash and dot (/.).

PoC

npm create vite@latest
cd vite-project/
cat "secret" > .env
npm install
npm run dev
curl --request-target /.env/. http://localhost:5173