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.
History

Thu, 05 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-130
References
Metrics threat_severity

None

threat_severity

Moderate


Wed, 04 Mar 2026 21:15:00 +0000

Type Values Removed Values Added
First Time appeared Apache
Apache activemq
Apache activemq All Module
Apache activemq Mqtt Module
Vendors & Products Apache
Apache activemq
Apache activemq All Module
Apache activemq Mqtt Module
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 04 Mar 2026 10:30:00 +0000

Type Values Removed Values Added
References

Wed, 04 Mar 2026 09:15:00 +0000

Type Values Removed Values Added
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.
Title Apache ActiveMQ, Apache ActiveMQ All Module, Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is not properly validated
Weaknesses CWE-190
References
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: apache

Published:

Updated: 2026-03-04T20:28:45.825Z

Reserved: 2025-11-21T20:44:42.659Z

Link: CVE-2025-66168

cve-icon Vulnrichment

Updated: 2026-03-04T09:15:41.385Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-04T09:15:54.757

Modified: 2026-03-04T18:08:05.730

Link: CVE-2025-66168

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-03-04T08:45:00Z

Links: CVE-2025-66168 - Bugzilla