# CVE-2025-66168: apache-activemq — Fixed in 5.19.2 ☕ ☕ Maven Not in CISA KEV MEDIUM severity # CVE-2025-66168 — apache-activemq MEDIUM CVE-2025-66168 is a medium-severity (CVSS 5.4) CWE-190 vulnerability in org.apache.activemq:apache-activemq. A fix is available for org.apache.activemq:apache-activemq — see the affected versions and patch details below. Apache ActiveMQ, Apache ActiveMQ All Module, Apache ActiveMQ MQTT Module: MQTT control packet remaining length field is not properly validated Also known asBIT-activemq-2025-66168[GHSA-c825-6ph3-4h84](/vulnerability/GHSA-c825-6ph3-4h84) Published Mar 4, 2026 Updated Oct 28, 2026 Affected 9 pkgs Patched 9 / 9 Exploits None indexed Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## Exploitation Status ### No confirmed exploitation observed yet - CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment. Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66168. ## EPSS Exploitation Probability [via FIRST.org ↗](https://www.first.org/epss/) 0.9%probability of exploitation in next 30 days Lower Risk0.00% Lower risk than most CVEs59th percentile — riskier than 59% of all scored CVEsHighest risk 0.00%0.46%0.91%1.37%0.1%0.9%May 26Sep 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## How urgent is this, really ## Where this sits among everything scored ## Real-World Exposure 9 pkgs affected ☕`org.apache.activemq:apache-activemq`☕`org.apache.activemq:apache-activemq`☕`org.apache.activemq:apache-activemq`☕`org.apache.activemq:activemq-all`☕`org.apache.activemq:activemq-all`☕`org.apache.activemq:activemq-all`☕`org.apache.activemq:activemq-mqtt`☕`org.apache.activemq:activemq-mqtt`+1 more Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems. ## 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://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt) [https://www.cve.org/CVERecord?id=CVE-2026-40046](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. ## Affected Packages 9 total 9 fixed Ecosystem Package Vulnerable range Fix ☕Maven `org.apache.activemq:apache-activemq` all versions 5.19.2`org.apache.activemq:apache-activemq:5.19.2` ☕Maven `org.apache.activemq:apache-activemq` ≥ 6.0.0&&< 6.1.9 6.1.9`org.apache.activemq:apache-activemq:6.1.9` ☕Maven `org.apache.activemq:apache-activemq` ≥ 6.2.0&&< 6.2.1 6.2.1`org.apache.activemq:apache-activemq:6.2.1` ☕Maven `org.apache.activemq:activemq-all` all versions 5.19.2`org.apache.activemq:activemq-all:5.19.2` ☕Maven `org.apache.activemq:activemq-all` ≥ 6.0.0&&< 6.1.9 6.1.9`org.apache.activemq:activemq-all:6.1.9` ☕Maven `org.apache.activemq:activemq-all` ≥ 6.2.0&&< 6.2.1 6.2.1`org.apache.activemq:activemq-all:6.2.1` ## Affected Products 1 product · 3 configurations Application `activemq`apache ≥ 6.0.0 && ≤ 6.1.8 1 version 6.2.0 ## Detection & mitigation playbook Open-source dependency 1. ### Detect Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.activemq:apache-activemq, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version. 2. ### Fix Update org.apache.activemq:apache-activemq to 5.19.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66168 is resolved across your whole dependency graph. 3. ### Workarounds Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process. ## Fixing This On Your OS If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project. Red HatModerate Workaround published by Red Hat > Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Source: [Red Hat security advisory for CVE-2025-66168](https://access.redhat.com/security/cve/cve-2025-66168) (CC BY 4.0) ## Frequently Asked Questions 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 cont O3 Security · Impact-Aware SCA ### Is CVE-2025-66168 in your dependencies? Find it across Maven, including transitive dependencies. [Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)