oss-security - CVE-2025-66168: Apache ActiveMQ, Apache ActiveMQ All Module, Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is not properly validated

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <08cf698e-47cc-a5db-4a7d-70791f12ec86@apache.org>
Date: Tue, 03 Mar 2026 17:26:01 +0000
From: "Christopher L. Shannon" <cshannon@...che.org>
To: oss-security@...ts.openwall.com
Subject: CVE-2025-66168: Apache ActiveMQ, Apache ActiveMQ All Module,
 Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is
 not properly validated 

Severity: 

Affected versions:

- Apache ActiveMQ (org.apache.activemq:apache-activemq) before 5.19.2
- Apache ActiveMQ (org.apache.activemq:apache-activemq) 6.0.0 before 6.1.9
- Apache ActiveMQ (org.apache.activemq:apache-activemq) 6.2.0 before 6.2.1
- Apache ActiveMQ All Module (org.apache.activemq:activemq-all) before 5.19.2
- Apache ActiveMQ All Module (org.apache.activemq:activemq-all) 6.0.0 before 6.1.9
- Apache ActiveMQ All Module (org.apache.activemq:activemq-all) 6.2.0 before 6.2.1
- Apache ActiveMQ MQTT Module (org.apache.activemq:activemq-mqtt) before 5.19.2
- Apache ActiveMQ MQTT Module (org.apache.activemq:activemq-mqtt) 6.0.0 before 6.1.9
- Apache ActiveMQ MQTT Module (org.apache.activemq:activemq-mqtt) 6.2.0 before 6.2.1

Description:

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.

Credit:

Gai Tanaka <641.work123@...il.com> (finder)

References:

https://activemq.apache.org/
https://www.cve.org/CVERecord?id=CVE-2025-66168

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.