Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:NSummary
CVE-2025-66168 is a medium-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Apache Activemq. Its CVSS base score is 5.4 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 47% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-66168 is an integer overflow vulnerability (CWE-190) in Apache ActiveMQ's MQTT protocol handling, stemming from improper validation of the remaining length field during decoding of malformed packets. This causes the broker to incorrectly compute the total remaining length and misinterpret the payload as multiple MQTT control packets, violating the MQTT v3.1.1 specification's restriction of the field to a maximum of 4 bytes. The issue affects Apache ActiveMQ versions before 5.19.2, 6.0.0 to 6.1.8, and 6.2.0, occurring only on established connections after authentication and solely impacting brokers with enabled MQTT transport connectors.
Attackers with low privileges (PR:L) can exploit this vulnerability over the network (AV:N) with low attack complexity and no user interaction required. By connecting as an authenticated client and sending crafted malformed MQTT packets, they trigger the integer overflow, leading to unexpected broker behavior when processing non-compliant payloads. This results in limited confidentiality and integrity impacts (C:L/I:L/A:N), with an overall CVSS v3.1 base score of 5.4, but no availability disruption.
Apache ActiveMQ security advisories recommend upgrading to fixed versions 5.19.2, 6.1.9, or 6.2.1 to mitigate the issue. A specific warning notes that 6.x users should upgrade to 6.2.4 or later, as the fix was missed in prior 6.x releases. Brokers without MQTT transport connectors remain unaffected. Additional details are available in the official announcement at https://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt and related CVE record at https://www.cve.org/CVERecord?id=CVE-2026-40046.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-208266
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.2.6
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (static analysis, fuzzing, unit tests) directly finds integer overflow defects before deployment.
Secure engineering principles require use of safe arithmetic constructs or language features that structurally eliminate integer overflow during calculation.
Input validation enforces bounds on values before arithmetic, stopping the conditions that trigger overflow or wraparound.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require use of safe arithmetic, bounds checks, and testing that prevent integer overflows.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect integer overflows before release.
Secure SDLC mandates input validation and arithmetic checks that prevent integer overflows.
Application security requirements include bounds checking and safe arithmetic to avoid overflow conditions.
Secure architecture principles require defensive coding patterns that mitigate integer wraparound risks.
Secure coding standards explicitly forbid unsafe integer operations and mandate overflow-safe constructs.