Apache ActiveMQ, Apache ActiveMQ All Module, Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is not properly validated

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Summary

CVECVE-2025-66168
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-04 09:15:54 UTC
Updated2026-04-10 11:16:21 UTC
DescriptionWARNING: 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.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.000690000 probability, percentile 0.211220000 (date 2026-04-15)

Problem Types: CWE-190 | CWE-190 CWE-190 Integer Overflow or Wraparound

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary8.8HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1[email protected]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
3.1CNACVSS5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Apache Activemq All All All All
Application Apache Activemq 6.2.0 All All All
Application Apache Activemq All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache ActiveMQ affected 5.19.2 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ affected 6.0.0 6.1.9 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ affected 6.2.0 6.2.1 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ All Module affected 5.19.2 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ All Module affected 6.0.0 6.1.9 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ All Module affected 6.2.0 6.2.1 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ MQTT Module affected 5.19.2 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ MQTT Module affected 6.0.0 6.1.9 semver Not specified
CNA Apache Software Foundation Apache ActiveMQ MQTT Module affected 6.2.0 6.2.1 semver Not specified

References

ReferenceSourceLinkTags
activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt [email protected] activemq.apache.org
www.openwall.com/lists/oss-security/2026/03/03/5 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
www.cve.org/CVERecord [email protected] www.cve.org
lists.apache.org/thread/13n8mkrb2jf2y6yyhpgrkmpqcm7djyto [email protected] lists.apache.org Mailing List, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Gai Tanaka <[email protected]> (en)

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