Vite dev server option `server.fs.deny` can be bypassed when hosted on case-insensitive filesystem

Summary

Vite dev server option server.fs.deny can be bypassed on case-insensitive file systems using case-augmented versions of filenames. Notably this affects servers hosted on Windows.

This bypass is similar to nvd.nist.gov/vuln/detail/CVE-2023-34092 -- with surface area reduced to hosts having case-insensitive filesystems.

Patches

Fixed in vite@5.0.12, vite@4.5.2, vite@3.2.8, vite@2.9.17

Details

Since picomatch defaults to case-sensitive glob matching, but the file server doesn't discriminate; a blacklist bypass is possible.

See picomatch usage, where nocase is defaulted to false: github.com/vitejs/vite/blob/v5.1.0-beta.1/packa…

By requesting raw filesystem paths using augmented casing, the matcher derived from config.server.fs.deny fails to block access to sensitive files.

PoC

Setup

1. Created vanilla Vite project using npm create vite@latest on a Standard Azure hosted Windows 10 instance.

   • npm run dev -- --host 0.0.0.0

   • Publicly accessible for the time being here: 20.12.242.81

2. Created dummy secret files, e.g. custom.secret and production.pem

3. Populated vite.config.js with

export default { server: { fs: { deny: ['.env', '.env.*', '*.{crt,pem}', 'custom.secret'] } } }

Reproduction

1. curl -s http://20.12.242.81:5173/@fs//

   • Descriptive error page reveals absolute filesystem path to project root

2. curl -s http://20.12.242.81:5173/@fs/C:/Users/darbonzo/Desktop/vite-project/vite.config.js

   • Discoverable configuration file reveals locations of secrets

3. curl -s http://20.12.242.81:5173/@fs/C:/Users/darbonzo/Desktop/vite-project/custom.sEcReT

   • Secrets are directly accessible using case-augmented version of filename

Proof Screenshot 2024-01-19 022736

Impact

Who

• Users with exposed dev servers on environments with case-insensitive filesystems

What

• Files protected by server.fs.deny are both discoverable, and accessible