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
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.
Other sources
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:
— IBM
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
maven/org.apache.activemq:activemq-mqttto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
maven/org.apache.activemq:activemq-allto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
maven/org.apache.activemq:apache-activemqto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
Apache ActiveMQto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
Apache ActiveMQ Allto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
Apache ActiveMQ MQTTto a version that resolves this vulnerability.Fixed in 6.2.4 - Upgrade
Upgrade
Apache ActiveMQto a version that resolves this vulnerability.Fixed in 5.19.2 - Upgrade
Upgrade
Apache ActiveMQ Allto a version that resolves this vulnerability.Fixed in 5.19.2 - Upgrade
Upgrade
Apache ActiveMQ MQTTto a version that resolves this vulnerability.Fixed in 5.19.2
Event History
Frequently Asked Questions
What is the severity of CVE-2026-40046?
CVE-2026-40046 has a high severity due to the potential for integer overflow or wraparound vulnerabilities in Apache ActiveMQ.
How do I fix CVE-2026-40046?
You can fix CVE-2026-40046 by upgrading to Apache ActiveMQ version 6.2.4.
What components are affected by CVE-2026-40046?
CVE-2026-40046 affects Apache ActiveMQ MQTT, ActiveMQ All, and the core Apache ActiveMQ package.
Is CVE-2026-40046 related to any previous vulnerabilities?
Yes, CVE-2026-40046 is related to the earlier vulnerability identified as CVE-2025-66168.
What types of attacks can CVE-2026-40046 enable?
CVE-2026-40046 can potentially enable attackers to exploit the MQTT control packet due to the missing validation of the remaining length field.