Bugcrowd Security Flash - Spring4Shell: What It Is and How To Address It @Bugcrowd

Uploaded January 2023 | Updated September 2026, 1 hour ago

On March 31st, 2022, a zero-day vulnerability found in the popular Java Web application development framework Spring put numerous Web applications at risk of a remote attack. The flaw, dubbed Spring4Shell and SpringShell, has caused a great deal of confusion over the past 24 hours as the security community tries to determine if the issue is in fact new, or related to older vulnerabilities.

As of March 31st, 2022, Spring has confirmed the zero-day vulnerability and has released Spring Framework versions to address it. The vulnerability impacts Spring MVC and Spring WebFlux applications running on JDK 9+.

In this brief Bugcrowd Security Flash video, Casey Ellis (Founder, Chairman, and CTO of Bugcrowd) and Adam Foster (Application Security Engineer at Bugcrowd) help clear up the confusion and answer questions such as:

What happened?
What are the vulnerabilities?
How serious is the flaw and how is it exploited?
What should you do to stay secure?
How can Bugcrowd help?

Bugcrowd Security Flash - Spring4Shell: What It Is and How To Address It

Hacking Your Resumé - w/Ricki Burke (@cybersecricki)

Introduction to AI & Machine Learning - w/InsiderPhD

Why I ❤️ Offensive Work and Why I 💔 Offensive Work - w/Thomas Dullien (@halvarflake)

$What are WebSockets? Unlike standard HTTP where every request needs a response, WebSockets create a persistent, bi-directional communication channel. Once opened, data flows freely in both directions without the heavy overhead of HTTP headers. Its the backbone of real-time chat apps, live gaming, and trading platforms. ⚙️ How it works: The magic starts with a standard HTTP handshake. The client sends a GET request with the headers Connection: Upgrade and Upgrade: websocket. If the server agrees, it responds with an HTTP 101 Switching Protocols status code. The connection stays open, and the protocol shifts from http:// to ws:// (or wss:// if encrypted via TLS). 🤝 💰 Why its a bug bounty goldmine: Devs often authenticate the initial handshake but forget to authorize the actual messages being passed back and forth. Opening windows for bug hunters. Traditional WAFs struggle to inspect persistent binary or custom-framed WS traffic. It’s essentially a dark tunnel straight to the backend logic, serving as a WAF bypass. 🏁 Top vulnerabilities: 1️⃣ CSWSH (Cross-Site WebSocket Hijacking): If the server relies solely on cookies for the handshake and ignores the Origin header, attackers can trick a victims browser into opening a WS connection and stealing their data. 2️⃣ IDOR & Unauth Access: Sending API commands (like {user_id: 1337, action: delete}) via WS without session validation. 3️⃣ Injection (XSS/SQLi): Dropping blind payloads into the WS stream that execute on an internal admin dashboard. 🛠️ Toolkit: You cant hack what you cant see. Here’s the toolkit to enhance your hunting: 👇 1. Burp Suite: The WebSockets History tab and Repeater are your best friends. Intercept, modify, and drop frames. 2. STEWS: A lethal tool for automated WS endpoint discovery and vulnerability fingerprinting. 3. Wscat: Perfect for quick, lightweight CLI testing and raw connection probing. 🔖 Save this for later and bag those P1s.$

Bugcrowds VRT: with Katie Paxton-Fear and Codingo

Bugcrowd Security Flash - The Kaseya REvil Attack Explained

How a Hacker Uses the Bugcrowd Platform with Brandon Reynolds

Bugcrowd Security Flash: The HackLore Project