Fixing the Apache ActiveMQ Remote Code Execution Vulnerability- CVE-2023-46604

Apache ActiveMQ is a popular open-source message broker software that enables asynchronous messaging between distributed systems and applications. It uses the OpenWire protocol to handle the communication and transmission of messages between producers and consumers.

Recently, a critical remote code execution (RCE) vulnerability CVE-2023-46604 was disclosed in certain versions of Apache ActiveMQ. This vulnerability allows an unauthenticated remote attacker to execute arbitrary code on vulnerable ActiveMQ server instances. If exploited, this vulnerability poses a severe risk as it can lead to full system compromise.

In this blog post, we will dive into the technical details of this RCE vulnerability, understand how it can be exploited, and most importantly- learn how to fix and mitigate it effectively.

What is Apache ActiveMQ?

Apache ActiveMQ is an open-source, multi-protocol messaging server written in Java together with a full Java Message Service (JMS) client. It supports advanced messaging features like message queues, publish-subscribe messaging, and temporal control over message delivery.

ActiveMQ provides asynchronous messaging services and acts as a middleware layer in distributed applications. It is commonly used for building event-driven and scalable cloud and enterprise systems by decoupling message producers from message consumers.

Popular programming language frameworks like Spring Boot integrate with ActiveMQ for adding messaging capabilities to applications. The lightweight broker is also often used in containers and microservices architectures.

Overview of CVE-2023-46604

Summary:

The RCE vulnerability arises due to improper deserialization of untrusted data in the OpenWire protocol implementation in ActiveMQ. By carefully manipulating serialized Java object data sent via OpenWire, an attacker can cause arbitrary code execution on the target system running the vulnerable ActiveMQ broker.

Specifically, the attacker can send maliciously crafted serialized data that will get deserialized by ActiveMQ and trigger the instantiation of any attacker-chosen class available in the classpath. This results in arbitrary code execution with the permissions of the user running the ActiveMQ server process.

The vulnerability announcement from Apache lists the affected versions of ActiveMQ as follows:

This is rated as a critical severity vulnerability with a CVSS base score of 10.0. If you are running an affected version of Apache ActiveMQ, it is recommended to urgently upgrade or apply mitigations to avoid getting compromised.

Several proof-of-concept exploits that leverage this vulnerability to achieve RCE have already been published. There are also reports of active exploitation in the wild.

Verifying Vulnerability Presence

The first step is to verify whether your Apache ActiveMQ installation is actually vulnerable to this RCE issue. Here are a few ways to check for the vulnerability:

If you have any instances of Apache ActiveMQ in the vulnerable version range, you should proceed to upgrade them or apply mitigations urgently.

Updating Apache ActiveMQ to Fix This Vulnerability

Apache ActiveMQ servers running the following vulnerable versions should be updated as soon as possible to the corresponding fixed releases:

General Upgrade Procedure

Step 1 – Back up the Existing Broker Instance

Before upgrading, you should back up your current Apache ActiveMQ installation including:

This will allow you to roll back cleanly in case any issues arise during the upgrade.

Step 2 – Install the New Apache ActiveMQ Version

Download the latest Apache ActiveMQ release archive from the official website that is greater than 5.15.16, 5.16.7, 5.17.6 or 5.18.3. Extract this archive to a fresh directory location. This new directory will act as the broker home for the upgraded instance.

Step 3 – Update the Broker Instance to Reference the New Home

The ActiveMQ instance links to the broker home via the ARTEMIS_HOME variable defined in artemis.profile. Update this variable to point to the new home directory extracted in Step 2.

Similarly, update any other scripts like artemis-service.xml on Windows to set ARTEMIS_HOME to the new home path.

Step 4 – Refresh Broker Scripts and Configuration Files

Consider using the upgrade helper tool provided by Apache to automatically refresh key scripts, config files, and properties like artemis.profile and log4j2.properties for the new version.

Review refreshed configs for any customizations that may need to be re-applied from the older backed-up files.

Step 5 – Restart the Broker

Finally, restart the Apache ActiveMQ broker service to load the new version and apply the upgrade changes. The broker home will now point to the new fixed release containing security fixes.

The bundled artemis upgradetool makes the upgrade easier by automatically refreshing instance scripts, configs, and properties to match the new version.

Customizations to older configs may need to be ported to the new refreshed files. The upgrade command itself copies older changed files to a old-config-bkp folder.

Refer to the official ActiveMQ upgrade guide for more detailed instructions on completing the upgrade process.

The developers have also provided an upgrade helper tool that can automate updates to key scripts and config files when transitioning an existing broker instance to a new ActiveMQ version. This tool can simplify the upgrade process.

Applying Additional Mitigations

If you are unable to upgrade immediately, you should apply restrictions on network access to the vulnerable ActiveMQ brokers while you plan an upgrade. Here are some steps to secure access in the interim:

Verifying the Fix

Once you have upgraded your ActiveMQ instances or applied mitigations, you should retest to verify that the vulnerability is no longer present.

Detecting Exploitation Attempts

It is also crucial to monitor production systems for any indicators of compromise associated with CVE-2023-46604 exploitation:

Conclusion

This recently disclosed high-severity RCE vulnerability in Apache ActiveMQ definitely warrants urgent attention. All organizations using vulnerable ActiveMQ versions in internet-facing environments should treat this as a critical priority and upgrade or apply mitigations immediately.

While upgrading to a newer fixed release is the best solution, the additional mitigations provide defense-in-depth and reduce risks until upgrades can be completed. Remember to validate remediation steps taken to ensure the vulnerability is fully addressed across all instances.

For any assistance with assessing your exposure or fixing this ActiveMQ vulnerability, do not hesitate to contact your security services provider. Please share any suspicious activity observed with the relevant security teams immediately for rapid detection and response.

We hope this post helps you know how to fix CVE-2023-46604, a remote code execution vulnerability in Apache ActiveMQ . Please share this post and help secure the digital world.Visit our website thesecmaster.com, and our social media page on Facebook, LinkedIn, Twitter, Telegram, Tumblr, Medium, and Instagram and subscribe to receive updates like this.

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