Apache ActiveMQ Vulnerability Lets Remote Hackers Execute Arbitrary Code

A high vulnerability in Apache ActiveMQ’s .NET Message Service (NMS) library has been uncovered, enabling remote attackers to execute arbitrary code on unpatched systems.

Tracked as CVE-2025-29953, this flaw carries a high CVSS score of 8.1 and impacts all versions of ActiveMQ before the latest security update.

Vulnerability Overview

The flaw resides in the Body accessor method of the NMS library, which fails to validate user-supplied data during deserialization.

This allows attackers to inject malicious payloads that bypass security checks, leading to remote code execution (RCE) within the context of the ActiveMQ process.

Key Risk Factors:

• No authentication required: Attackers can exploit this remotely without credentials.
• Widespread impact: ActiveMQ is widely used in enterprise messaging systems, IoT, and cloud infrastructure.
• Variable attack vectors: Exploitation methods depend on how the NMS library is implemented in specific environments.

Apache patched the issue in an April 30, 2025, update after a coordinated disclosure process involving cybersecurity firm Zero Day Initiative (ZDI), which first reported the flaw in November 2023.

How the Exploit Works

Deserialization vulnerabilities occur when untrusted data is converted into executable code. In this case, the NMS library’s improper handling of serialized objects in message bodies allows attackers to:

1. Craft malicious messages targeting the Body property.
2. Trigger deserialization of these messages on the server.
3. Execute arbitrary commands, potentially leading to full system compromise, data theft, or ransomware deployment.

The exploit requires no user interaction, making it particularly dangerous for internet-facing ActiveMQ instances.

Mitigation and Recommendations

Apache urges all users to immediately update to the latest ActiveMQ version, which includes validation checks for serialized data. Additional safeguards include:

1. Restrict network exposure: Ensure ActiveMQ instances are not publicly accessible unless necessary.
2. Monitor logs: Watch for unusual activity, such as unexpected deserialization errors or inbound connections from unknown IPs.
3. Review integrations: Audit custom implementations using the NMS library for potential exposure.

This vulnerability underscores persistent risks in messaging systems, which often act as critical backend infrastructure.

“Deserialization flaws are among the most lethal attack vectors,” warns ZDI analyst Mark Rivers. “Organizations must prioritize patch management and network segmentation to mitigate such threats.”

With ActiveMQ powering systems in healthcare, finance, and logistics, unpatched servers could face disruptive attacks akin to the 2021 Log4j crisis.

Administrators are advised to act swiftly, as proof-of-concept exploits for similar vulnerabilities often emerge within days of public disclosure.