CVE-2025-66168 Apache ActiveMQ is Vulnerable to Integer Overflow or Wraparound

What is CVE-2025-66168?

CVE-2025-66168 is a medium-severity vulnerability in Apache Activemq, published on 4 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

WARNING:

Users of 6.x should upgrade to 6.2.4 or later as the fix was missed in previous 6.x releases.

See the  following for more details: https://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt https://www.cve.org/CVERecord?id=CVE-2026-40046

Original Report:

Apache ActiveMQ does not properly validate the remaining length field which may lead to an overflow during the decoding of malformed packets. When this integer overflow occurs, ActiveMQ may incorrectly compute the total Remaining Length and subsequently misinterpret the payload as multiple MQTT control packets which makes the broker susceptible to unexpected behavior when interacting with non-compliant clients. This behavior violates the MQTT v3.1.1 specification, which restricts Remaining Length to a maximum of 4 bytes. The scenario occurs on established connections after the authentication process. Brokers that are not enabling mqtt transport connectors are not impacted.

This issue affects Apache ActiveMQ: before 5.19.2, 6.0.0 to 6.1.8, and 6.2.0

Users are recommended to upgrade to version 5.19.2, 6.1.9, or 6.2.1, which fixes the issue.

Weakness: CWE-190

Which versions are affected by CVE-2025-66168?

19 open source packages ship an affected version, including org.apache.activemq:activemq-all, activemq and org.apache.activemq:activemq-mqtt. It affects 1 product.

Products include Apache Activemq.

How do I fix CVE-2025-66168?

Upgrade org.apache.activemq:activemq-all to a fixed version for your release line: 5.19.2, 6.1.9 or 6.2.1.

Is CVE-2025-66168 being exploited?

There is no known exploitation of CVE-2025-66168 in the wild and no public exploit code.

Other vulnerabilities in Apache Activemq

• CVE-2023-46604 Apache ActiveMQ Deserialization of Untrusted Data Exploited Critical 10.0
• CVE-2016-3088 Apache ActiveMQ Improper Input Validation Exploited Critical 9.8
• CVE-2026-34197 Apache ActiveMQ Improper Input Validation Exploited High 8.8
• CVE-2020-11998 Remote code execution in Apache ActiveMQ Critical 9.8
• CVE-2013-7285 Command Injection in Xstream Critical 9.8

All Apache Activemq vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-activemq-2025-66168, DEBIAN-CVE-2025-66168, GHSA-c825-6ph3-4h84, MINI-5r4w-mrf3-qx8x, MINI-97j5-568x-vw27, MINI-fx38-h72q-qmh9 and 11 more.