Hello everyone, this is an article or summary about the CVE-2025-36041 vulnerability and the IBM MQ service based on my research and detailed analysis of the service architecture:
Link : https://nvd.nist.gov/vuln/detail/CVE-2025-36041 
Introduction to IBM MQ

First, before discussing the vulnerability or anything else, let’s understand what IBM MQ actually is:

IBM MQ is an Enterprise Messaging System used to provide a reliable and efficient communication channel between different applications, whether these applications run on the same machine or across a wide network.

But why do we need to use this service in the first place?

In today’s software world, applications are often complex and distributed systems, meaning they consist of multiple parts running on different systems and possibly in different programming languages. To achieve cooperation between these parts, applications need to exchange messages or data in an organized and reliable manner, and this is where IBM MQ comes in. Instead of applications relying on direct and synchronous communication, IBM MQ provides an asynchronous messaging system, so that:

The application sends a message to a queue inside IBM MQ.

The message is temporarily stored until the receiving application can receive and process it at the appropriate time.

This ensures the continuity of application operation even if some parts are disconnected or busy.

-> Core features of IBM MQ:

Reliability: Guarantees message delivery even if the system crashes or the connection is lost.

Scalability: Supports large and complex environments such as banks and insurance companies that require processing millions of messages daily.

Security: Supports encryption (SSL/TLS) and authentication to ensure data and communication protection.

Compatibility: Works with multiple operating systems (Windows, Linux, Unix, etc.) and offers diverse APIs like MQI and JMS.

Independence: Uses various protocols to ensure security and service compatibility such as JMS, MQI, MQ over TCP.
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=mq-technical-overview

Explanation of IBM MQ Protocols:

MQI – Message Queue Interface:

MQI is a protocol and API specific to IBM MQ, providing a standard way for applications to create, send, receive, and manage messages inside IBM MQ queues. MQI uses a set of functions that allow the application to connect to the Queue Manager, create message queues, send and receive messages, and handle errors. It has many features including:

Supports programming in multiple languages like C, C++, Java, and .NET.

Manages the connection between the application and IBM MQ at a very low level, providing high control.

Flexible and customizable according to the application's needs.
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=queuing-message-queue-interface-overview
-> JMS – Java Message Service:

JMS is a Java API standard that enables synchronous or asynchronous message sending and receiving across messaging systems. IBM MQ fully supports JMS to integrate Java applications with the messaging system.

JMS provides an abstraction layer allowing Java applications to interact with IBM MQ via concepts like Queues and Topics without
Link (JMS) : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=interfaces-mq-classes-jms
needing to know the underlying protocol details. It has many advantages such as:

Easy to use for Java applications.

Supports different messaging models (Point-to-Point via Queue, or Publish/Subscribe via Topic).

Simplifies message management in Java environments.

-> MQ over TCP/IP:

This is the core protocol used by IBM MQ to transfer messages over the network. Simply put, IBM MQ uses TCP/IP as a secure and reliable transport method between the Queue Manager and applications. IBM MQ opens specific ports (default port 1414) to communicate over TCP, where data packets containing messages are sent, with guaranteed correct and ordered delivery. It features:

Reliance on the well-known reliable TCP protocol.

Can be secured using SSL/TLS to encrypt communications.

Allows communication between different and diverse systems over the network.

Of course, in addition to TCP/IP, there is the MQ over SSL/TLS protocol whose purpose is to encrypt and ensure the security and reception of messages in encrypted form. These are the main protocols used by the IBM MQ service.
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=application-sharing-tcpip-connection-in-mq-classes-jms

-> IBM MQ Architecture: 

Queue Manager Architecture:

- Queue Manager (QMGR):

This is the central daemon or process responsible for managing queue states, handling client sessions, scheduling messages, and executing transactions. It acts as a broker coordinating system components.

- Process Model:

IBM MQ relies on an architecture consisting of multiple threads and processes:

Listener Process: waits for connection requests on TCP/IP ports.

Channel Initiator (CHIN): manages channel startup and connection settings.

Message Channel Agent (MCA): a subprocess for each channel responsible for sending and receiving data.

Inter-Process Communication (IPC):

Within the QMGR components, MQ uses advanced mechanisms like shared memory segments and semaphores to exchange state and message data.

-> Queues Data Structures:

- Message Descriptor (MQMD):
Link : https://www.ibm.com/docs/en/ibm-mq/9.3.x?topic=mqi-mqmd-message-descriptor
Each message contains a data header (MQMD) including metadata such as Message ID, Correlation ID, Priority, Persistence, Expiry Time, etc., which defines the message’s behavior inside the system.

- Queue Control Blocks (QCB):

Data structures inside the Queue Manager representing queues, containing pointers such as:

Head and Tail pointers for queue messages.

Counters for the number of messages.

Flags to determine status (open, locked, restricted).

Linked List of Messages:

Inside each queue, messages are stored in a linked list with pointers to navigate between them, ensuring high performance in insertion and deletion operations.

-> Channels Protocol Stack:

- Base Protocol:

IBM MQ channels use a unified transport protocol based on TCP/IP, with application layers dedicated to message handling.

Message Channel Agent (MCA) Protocol:

A protocol layer dedicated to managing connections between Queue Managers or between Client and Queue Manager. It includes:

Handshake Phase: negotiation of protocol version, encryption features, packet size, and error management.

Data Transfer Phase: streaming of message data over TCP with message packet fragmentation and reassembly.

Flow Control: a window-based flow control mechanism to prevent congestion and ensure QoS.

- Security Layer (TLS/SSL):
Link: https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=overview-security-in-mq
The encryption layer uses the TLS standard (usually TLS 1.2 or 1.3) to secure channels, supporting authentication protocols like X.509 certificates.

-> Channel Types:
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=explorer-channels
Sender-Receiver: for QMGR-to-QMGR channels.

Server-Client: for Client-to-QMGR channels.

Request-Reply: supports synchronous request/response patterns.

Cluster Sender/Receiver: for cluster channels.

-> Message Delivery Mechanisms:

Persistent vs Non-Persistent Messaging:

Persistent: messages are written to log files before confirming receipt, ensuring no loss even if the system crashes.

Non-Persistent: stored in memory, faster but prone to loss.

Transactional Integrity:

-> IBM MQ supports Distributed Transaction Processing (DTP) protocols such as:

XA Transactions: coordinated by an external Transaction Manager.

Unit of Work (UOW): grouping several message operations as a single work unit.

-> Message Grouping:
Link : https://www.ibm.com/docs/sv/ibm-mq/9.2.x?topic=messages-message-groups 
Supports grouping messages into meaningful sets with control over delivery order and failure handling.

Message Priority & Scheduling:

Messages can have priorities (0-9), and the Queue Manager uses scheduling tables to ensure higher priority messages are delivered first.

-> Storage Subsystem:

- Log-Based Storage:
Link : https://www.ibm.com/docs/en/ibm-mq/9.3.x?topic=configuration-queue-manager-storage  

MQ uses a log system modified for storing persistent messages, relying on:

Circular logs: rotating files upon reaching a specified size.

Checkpointing: ensuring message and data state stability on disk.

Page Caching:

Uses page cache memory to speed up message read/write operations.

File System Interaction:

MQ depends on local or specialized file systems, supporting advanced file systems like ZFS or GPFS (in enterprise environments).

Synchronization & Concurrency Control:

-> Locking Mechanisms:

MQ uses advanced locking such as reader-writer locks and mutexes to control concurrent access to queues and messages.

Semaphore & Event Signals:

Used to signal arrival of new messages or state changes, increasing resource consumption efficiency.

-> Thread Pools:

Manages pools of threads processing messages in parallel without affecting system performance.

- API Layers & Client Interactions:
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=mq-technical-overview 

- MQI (Message Queue Interface):
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=queuing-message-queue-interface-overview

A core API layer in C/C++ providing sending, receiving, and message management operations with advanced transactional and messaging capabilities.

- JMS (Java Messaging Service):

A higher-level abstraction based on MQI, offering a standard Java interface for developers.

- MQSC (MQ Script Command):

A command-line tool for managing and configuring Queue Managers, queues, and channels.

- MQ REST API:

A modern RESTful HTTP-based interface enabling control and interaction with IBM MQ via web applications.

Security Architecture:

- TLS Handshake and Certificate Validation:

IBM MQ uses TLS handshake to validate X.509 certificates, with options to restrict cipher suites, encryption keys, and certificate validity.

An advanced rule system controls channels, allowing restrictions by IP address, channel name, user, or other properties.

Access Control Lists (ACLs):

Manages fine-grained permissions on resources (Queues, Channels, Topics) at the Queue Manager level.

Integration with External Security Services:

- Supports integration with LDAP, Kerberos, RADIUS, enabling centralized and strong authentication.

High Availability & Scalability:

-> Queue Manager Clustering:
Link : https://www.ibm.com/docs/en/ibm-mq/9.3.x?topic=explorer-queue-manager-clusters
A cluster system allows resource replication, load distribution, and automatic message routing among nodes.

Multi-instance Queue Managers:

Ensures multiple active QMGR instances on different servers with automatic failover.

-> Load Balancing:
Link : https://www.ibm.com/docs/en/ibm-mq/9.2.x?topic=commands-workload-balancing-in-clusters

Via multiple channels and mirrored queues to distribute message traffic and reduce failure points.

Monitoring & Diagnostics:

Instrumentation APIs:

APIs to capture performance metrics and real-time system status.

Trace & Dump Facilities:

Advanced mechanisms to generate detailed reports on ongoing operations, errors, and message flow.

Event Notifications:

Supports event notifications via MQ Events and integration with SIEM systems or external monitoring.

-> CVE-2025-36041 in IBM MQ:

After knowing the service architecture and everything, let’s look at the vulnerability.

The CVE-2025-36041 vulnerability is a security flaw in the IBM MQ Channels Authentication mechanism related to SSL/TLS certificate validation when establishing connections between Client and Queue Manager or between Queue Managers.

In IBM MQ environments, communication channels relying on SSL/TLS secure data transport are used. When a channel is set to be authenticated, the Queue Manager must verify the client’s certificate before accepting the connection.

The vulnerability appears in channels that allow “unauthenticated” connections or when verification conditions are weak, such that:

An attacker can send a forged or invalid SSL certificate,

But the Queue Manager wrongly accepts the connection without sufficient verification. Here lies the vulnerability, allowing bypassing the identity verification of the other party (Client or QMGR).

Exploitation stages:

The attacker needs the ability to connect to the IBM MQ network, either via local network or via the internet if the service is exposed directly.

-> Steps:

Configure a connection channel with the Queue Manager to be either unauthenticated or with lax verification settings.

Send a forged or manipulated certificate that appears valid or is accepted inaccurately.

Due to a flaw in IBM MQ’s verification mechanism, the connection is accepted.

After acceptance, the attacker can establish a channel with privileges that might allow reading or sending messages to sensitive queues, or modifying them.

What can the vulnerability cause?

The vulnerability’s severity is moderate (CVSS v3.0), meaning it’s not critical, but it can be leveraged for several things such as:

Allowing the attacker to create unauthenticated channels, enabling them to:

Send forged messages.

Read confidential or sensitive messages from queues.

Disrupt the messaging system or inject malicious data (Integrity Violation).

The vulnerability can be exploited in other attacks such as eavesdropping, Denial of Service (DoS), or executing malicious code in some scenarios.

How to mitigate the vulnerability risks?

Official Update:

Update to the latest IBM MQ version containing fixes for this vulnerability, where certificate verification mechanisms have been strengthened.

Channel Settings Tightening:

Enable strict SSL/TLS authentication for all channels, especially Client-Server and QMGR-QMGR channels.

Disable or remove all “unauthenticated” channels entirely.

Configure Channel Authentication Records to reject any connection without a valid certificate.

SSL/TLS Certificates Review:

Use valid certificates and periodically verify certificate chains and validity.

Monitoring and Alerts:

Check Queue Manager logs for unauthenticated connection attempts or repeated warnings.

Set security alerts for any suspicious activity.