CVE-2026-40046: Apache ActiveMQ, Apache ActiveMQ All, Apache ActiveMQ MQTT: Missing fix for CVE-2025-66168: MQTT control packet remaining length field is not properly validated

["Christopher L. Shannon" <cshannon () apache org>]

Severity: moderate 

Affected versions:

- Apache ActiveMQ (org.apache.activemq:apache-activemq) 6.0.0 before 6.2.4
- Apache ActiveMQ All (org.apache.activemq:activemq-all) 6.0.0 before 6.2.4
- Apache ActiveMQ MQTT (org.apache.activemq:activemq-mqtt) 6.0.0 before 6.2.4

Description:

Integer Overflow or Wraparound vulnerability in Apache ActiveMQ, Apache ActiveMQ All, Apache ActiveMQ MQTT.

The fix for "CVE-2025-66168: MQTT control packet remaining length field is not properly validated" was only applied to 
5.19.2 (and future 5.19.x) releases but was missed for all 6.0.0+ versions.


This issue affects Apache ActiveMQ: from 6.0.0 before 6.2.4; Apache ActiveMQ All: from 6.0.0 before 6.2.4; Apache 
ActiveMQ MQTT: from 6.0.0 before 6.2.4.



Users are recommended to upgrade to version 6.2.4 or a 5.19.x version starting with 5.19.2 or later (currently latest 
is 5.19.5), which fixes the issue.

Credit:

Adrien Bernard (finder)

References:

https://www.cve.org/CVERecord?id=CVE-2025-66168
https://activemq.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-40046