High severity · published Apr 9, 2026
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
7.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AC
ActiveMQ · Apache
6.0.0 before 6.2.4 · source: vendor
AA
Apache ActiveMQ All · Apache Software Foundation
6.0.0 before 6.2.4 · source: vendor
AA
Apache ActiveMQ MQTT · Apache Software Foundation
6.0.0 before 6.2.4 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40046
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40046
activemq.apache.org
https://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt
lists.apache.org
https://lists.apache.org/thread/zdntj5rcgjjzrpow84o339lzldy68zrg
www.cve.org
https://www.cve.org/CVERecord?id=CVE-2025-66168
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