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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2025-66168)

Note that Nessus relies on the presence of the package as reported by the vendor.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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. (CVE-2025-66168)

The version of Apache ActiveMQ running on the remote host is prior to 5.19.2, 6.0.x prior to 6.1.9, or 6.2.0. It is, therefore, affected by a vulnerability:

  - Apache ActiveMQ does not properly validate the remaining length field in MQTT control packets which may     lead to an integer 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.
    (CVE-2025-66168)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
301143	Linux Distros Unpatched Vulnerability : CVE-2025-66168	Nessus	Misc.	high
438353	SCA: security update for org.apache.activemq:activemq-all, org.apache.activemq:activemq-mqtt, org.apache.activemq:apache-activemq (GHSA-c825-6ph3-4h84)	Tenable Cloud Security	SCA Checks	high
438353	SCA: security update for org.apache.activemq:activemq-all, org.apache.activemq:activemq-mqtt, org.apache.activemq:apache-activemq (GHSA-c825-6ph3-4h84)	Tenable Self-Hosted Container Security	SCA Checks	high
300913	Apache ActiveMQ < 5.19.2 / 6.0.x < 6.1.9 / 6.2.0 MQTT Control Packet Validation Vulnerability (CVE-2025-66168)	Nessus	CGI abuses	high

Detections

Analytics

CVE-2025-66168

high

Tenable Plugins

high

high

high

high