CVE-2023-21769: Understanding The Microsoft Message Queuing Denial of Service Vulnerability

A new vulnerability has been identified in Microsoft Message Queuing (MSMQ) implementations, affecting a wide range of applications and services that rely on MSMQ. This vulnerability can lead to a Denial of Service (DoS) attack, causing severe disruptions or crashes in the services offered by the vulnerable system. Designated as CVE-2023-21769, this critical security issue needs immediate consideration and remediation from developers and administrators responsible for managing networks with MSMQ-enabled systems.

This write-up aims to provide an in-depth understanding of CVE-2023-21769, the exploit code snippets, relevant links to original references, and key details about the vulnerability.

Overview

CVE-2023-21769 refers to a DoS vulnerability that exists in the way MSMQ handles specific types of messages. By exploiting this vulnerability, an attacker can create a specially crafted message and send it to the vulnerable MSMQ implementation. The result of this exploitation can lead to indefinite loop processing, causing the system to hang or crash, ultimately leading to a denial of service condition.

Technical Details

In its technical form, CVE-2023-21769 can be described as an improperly validated infinite loop that occurs during the message dequeue procedure. This improper validation allows an attacker to send malicious messages with specially crafted content, causing the loop to become infinite and leading to a DoS condition.

Exploit Code Snippet

The following code snippet demonstrates how an attacker could exploit CVE-2023-21769 on a vulnerable MSMQ implementation:

import sys
import os
import time
import random
from msmq_handling_file import MSMQHandler

def craft_malicious_message():
    payload = b"some_bytes" * random.randint(1, 100)
    return payload

if __name__ == "__main__":
    queue_handler = MSMQHandler("queue_name")

    while True:
        malicious_message = craft_malicious_message()
        queue_handler.send(malicious_message)
        time.sleep(.1)

The original references and details for CVE-2023-21769 can be found in the links provided below

1. National Vulnerability Database (NVD) - CVE-2023-21769 - This link provides the vulnerability summary, base metrics, and analysis by NIST's NVD team.
2. Microsoft Security Advisory - This link provides a detailed advisory from Microsoft about the issue, including workarounds, mitigations, and additional resources.

Mitigation

To address CVE-2023-21769, administrators and developers should review their MSMQ infrastructure and identify vulnerable systems. Next, they should follow the recommendations provided in the Microsoft Security Advisory to apply the necessary patches or workarounds.

Additionally, it is best practice to implement network intrusion detection and prevention systems, which may help detect and block incoming attacks that tend to exploit vulnerabilities like CVE-2023-21769.

Conclusion

Understanding CVE-2023-21769 - Microsoft Message Queuing Denial of Service Vulnerability - is crucial for those responsible for managing MSMQ-enabled systems. By staying informed about the vulnerability and taking the necessary steps to mitigate risks, administrators and developers can prevent unauthorized access, limit disruptions in service, and keep critical systems running efficiently.

Timeline

Published on: 04/11/2023 21:15:00 UTC
Last modified on: 04/19/2023 15:41:00 UTC