## https://sploitus.com/exploit?id=90266A40-3D62-5352-B48D-345B3A488EC6
# Python Firewall for Spring4Shell (CVE-2022-22965) Mitigation
## 1. Overview
This project is a simple but effective firewall implemented as a Proof-of-Concept (POC) in Python. It's designed to act as an HTTP server that inspects incoming POST requests to detect and block the specific payload pattern associated with the Spring4Shell (CVE-2022-22965) remote code execution (RCE) vulnerability.
## 2. How It Works
The firewall leverages Python's built-in `http.server` module. The core logic resides in the `do_POST` method of the `ServerHandler` class.
1. The server intercepts all incoming `POST` requests.
2. It reads the entire request body.
3. It searches for the malicious signature string: `class.module.classLoader`. This string is the fundamental component of the Spring4Shell exploit and is difficult for an attacker to obfuscate.
4. **If the pattern is found**, the server immediately blocks the request by sending a `403 Forbidden` HTTP response.
5. **If the pattern is not found**, the request is considered legitimate and is handled normally with a `200 OK` response.
## 3. Why This Approach?
While other mitigation strategies could focus on headers or specific URL paths, this method was chosen for its robustness:
* **Resilient:** It is not dependent on fragile indicators like filenames (e.g., `tomcatwar.jsp` ) or custom header names, which can be easily changed by an attacker.
* **Effective:** It targets the core mechanism of the exploit itself, making it a highly reliable detection method against this specific vulnerability.
## 4. Usage
To run the firewall, use the main script [`firewall_server.py`](firewall_server.py):
```bash
python firewall_server.py
```
The server will start on localhost:8000.
You can then use the provided [`Test_Requester.py`](Test_Requester.py) script to simulate malicious requests and verify that they are being blocked.
## 5. Disclaimer
This is a Proof-of-Concept and is intended for educational and demonstrative purposes only. It is not a production-ready firewall solution.