CVE-2025-66168Apache ActiveMQ, Apache ActiveMQ All Module, Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is not properly validated
- 5.4MediumCVSS base score
- 0.87%Exploitation in 30 daysEPSS · top 41% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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: 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.
Timeline
ID reserved
By apache
- 3 months later
· 3 months later
Published
- 37 days later
· 37 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| apacheCNA (assigner) | 3.1 | Medium5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N |
| NVDNVD · Modified | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.87% · top 41% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.4.
Affected products
Apache Software Foundation · Apache ActiveMQ
- affected < 5.19.2
- affected 6.0.0 – < 6.1.9
- affected 6.2.0 – < 6.2.1
Apache Software Foundation · Apache ActiveMQ All Module
- affected < 5.19.2
- affected 6.0.0 – < 6.1.9
- affected 6.2.0 – < 6.2.1
Apache Software Foundation · Apache ActiveMQ MQTT Module
- affected < 5.19.2
- affected 6.0.0 – < 6.1.9
- affected 6.2.0 – < 6.2.1
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Mavenorg.apache.activemq:activemq-allGHSA-c825-6ph3-4h84 (opens in a new tab)
- Mavenorg.apache.activemq:activemq-mqttGHSA-c825-6ph3-4h84 (opens in a new tab)
- Mavenorg.apache.activemq:apache-activemqGHSA-c825-6ph3-4h84 (opens in a new tab)
References
References4
- https://lists.apache.org/thread/13n8mkrb2jf2y6yyhpgrkmpqcm7djyto (opens in a new tab)vendor-advisory
- https://www.cve.org/CVERecord?id=CVE-2026-40046 (opens in a new tab)related
- https://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt (opens in a new tab)related
- http://www.openwall.com/lists/oss-security/2026/03/03/5 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-208266 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-c825-6ph3-4h84 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-66168)Record last updated .