WebSocket Pentesting Guide: Attacks, Tools & Fixes

What Is WebSocket? ⚡​

WebSocket is a modern communication protocol that allows real-time, full-duplex communication between a client and a server over a single TCP connection.
Unlike HTTP, which works on a request/response model, WebSocket keeps the connection open. This means data can flow instantly in both directions with very low latency 🚀.

WebSocket is commonly used in:

• 💬 Real-time chat applications
• 📊 Live stock and crypto prices
• ⚽ Live sports scores
• 🎮 Online multiplayer games

In short: faster updates, smoother experience, and real-time data delivery.

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Why WebSocket Pentesting Matters 🔥​

WebSockets often bypass traditional HTTP security controls, such as:

• Web Application Firewalls (WAFs)
• CSRF protections
• Standard request-based security checks

Because of this, WebSocket endpoints are a high-value target for attackers 👀.
That’s why WebSocket pentesting should always be included in any serious web security assessment.

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WebSocket Pentesting Methodology 🧠​

Discovering WebSocket Endpoints 🔍​

The first step is identifying where WebSockets are used in the application.
Useful tools:

• Burp Suite → WebSockets tab
• Browser DevTools → Network → WS

Look for URLs like:

ws://example.com/socket
wss://example.com/socket

Always prefer wss://, since it uses encryption 🔐.

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Analyzing the WebSocket Handshake 🤝​

Before a WebSocket connection is established, a handshake takes place.
Example handshake request:

GET /socket HTTP/1.1
Host: example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13

What to check here:

• Missing or weak security headers
• Improper Origin validation
• Misconfigured upgrade handling

Any mistake in this phase can lead to serious vulnerabilities ⚠️.

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Common WebSocket Vulnerabilities 🧨​

Missing Authentication or Authorization ❌​

Try sending WebSocket messages without logging in.
If the server accepts them, that’s a critical issue 🚨.
Test ideas:

• Remove the authentication token
• Reuse another user’s token

Insecure Message Structure 🧩​

WebSocket messages are usually sent as JSON, making them easy to manipulate.
Example message:

{ "action": "getUserData", "userID": "123" }

Try changing userID and observe the response.
If you get another user’s data → vulnerability found.

IDOR (Insecure Direct Object Reference) 🔓​

If you can access or modify resources just by changing IDs, you’re dealing with IDOR.
Example payload:

{ "action": "deleteMessage", "messageID": "456" }

Guess different messageID values and test the results.

Command Injection or Code Execution 💀​

Poor input validation can allow attackers to inject commands.
Test payload example:

{ "username": "admin'; system('ls'); //" }

If the server executes this, the impact is severe 😬.

Sensitive Data Exposure 📡​

Some WebSocket servers broadcast messages to all connected clients.
Always monitor:

• Broadcast responses
• Background messages

Check if sensitive data like emails, tokens, or internal IDs are exposed.

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Improper Origin Validation (CSRF Risk) 🌍​

WebSocket servers must validate the Origin header.
Test scenario:

• Send a handshake request with a fake Origin
• If the connection succeeds → CSRF via WebSocket is possible

Denial of Service via Message Flooding 💣​

WebSockets can be abused for DoS attacks by flooding the server with messages.
Example Python test:

from websocket import create_connection

ws = create_connection("ws://example.com/socket")
for i in range(1000):
    ws.send("A" * 10000)

If the server slows down or crashes, it’s vulnerable.

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Best Tools for WebSocket Pentesting 🧰​

Tool	Purpose
Burp Suite	Intercept and modify WebSocket traffic
OWASP ZAP	WebSocket fuzzing
wscat	CLI WebSocket client
websocat	Advanced WebSocket testing
Python scripts	Custom automation and attacks

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Practical WebSocket Testing with wscat ⚙️​

Install wscat​

npm install -g wscat

Connect to the WebSocket​

wscat -c ws://example.com/socket

Send a Test Message​

{ "action": "getUserData", "userID": "1" }

Simple, fast, and extremely effective 👌.

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WebSocket Security Best Practices 🔐​

To properly secure WebSocket implementations:

• Always require authentication
• Validate and sanitize all input
• Apply rate limiting
• Avoid broadcasting sensitive data
• Enforce wss:// only
• Strictly validate the Origin header

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Final Thoughts 🎯​

WebSockets provide powerful real-time capabilities, but they also introduce unique security risks.
Every WebSocket endpoint should be treated as a critical attack surface and tested thoroughly during penetration testing engagements.
Ignoring WebSocket security can easily lead to data leaks, account takeover, or full system compromise 🔥.