What is the CVSS score of EUVD-2026-20956?

EUVD-2026-20956 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.0%.

Which versions of Apache are affected by EUVD-2026-20956?

Apache ActiveMQ versions 6.0.0 through 6.2.3 contain a remote denial-of-service vulnerability in the MQTT broker that allows unauthenticated attackers to crash the service via malformed control…. A patch is available.

How to fix or mitigate EUVD-2026-20956?

Within 24 hours: Identify all ActiveMQ instances running versions 6.0.0-6.2.3 via inventory scan and document MQTT broker exposure. Within 7 days: Implement network-level access controls to restrict MQTT protocol traffic (port 1883/8883) to trusted sources only, and monitor ActiveMQ logs for malformed packet attempts. Within 30 days: Upgrade to Apache ActiveMQ 6.2.4 or later once released, or migrate to version 5.19.x with the previously applied CVE-2025-66168 patch if immediate remediation is required.

Apache EUVD-2026-20956

| CVE-2026-40046 HIGH

Integer Overflow or Wraparound (CWE-190)

2026-04-09 apache

GHSA-xvqc-pp94-fmpx

Apache Integer Overflow Buffer Overflow Red Hat

7.5

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Red Hat

5.4 MEDIUM

qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Patch released

Apr 10, 2026 - 20:30 nvd

Patch available

EUVD ID Assigned

Apr 09, 2026 - 16:30 euvd

EUVD-2026-20956

Analysis Generated

Apr 09, 2026 - 16:30 vuln.today

CVE Published

Apr 09, 2026 - 15:58 nvd

HIGH 7.5

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

6 maven packages depend on org.apache.activemq:activemq-all (3 direct, 3 indirect)
6 maven packages depend on org.apache.activemq:activemq-mqtt (5 direct, 1 indirect)

Ecosystem-wide dependent count for version 6.0.0 and other introduced versions.

DescriptionCVE.org

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.

AnalysisAI

Remote denial-of-service in Apache ActiveMQ 6.0.0 through 6.2.3 allows unauthenticated network attackers to crash the MQTT broker via malformed control packets. An integer overflow in the MQTT protocol handler's remaining length field validation enables resource exhaustion without authentication. This vulnerability stems from an incomplete patch - the fix for CVE-2025-66168 was applied only to 5.19.x branches but omitted from all 6.x releases until 6.2.4. No public exploit identified at time of analysis. Low observed exploitation activity (EPSS 0.02%).

Technical ContextAI

CWE-190 integer overflow occurs when parsing MQTT control packet remaining length field. Validation logic introduced for CVE-2025-66168 was not ported to 6.x codebase, allowing malformed packets to trigger wraparound conditions in memory allocation routines, causing broker process termination. CVSS vector PR:N confirms unauthenticated remote attack surface.

RemediationAI

Vendor-released patch: upgrade to Apache ActiveMQ 6.2.4 or later for all 6.x deployments. Users on legacy 5.x branches must upgrade to 5.19.2 or later (latest: 5.19.5). No workarounds documented; patching is the only validated mitigation. If immediate upgrade is infeasible, disable MQTT transport connector in activemq.xml configuration to eliminate attack surface. Official advisory: https://activemq.apache.org/security-advisories.data/CVE-2026-40046-announcement.txt. Mailing list discussion: https://lists.apache.org/thread/zdntj5rcgjjzrpow84o339lzldy68zrg. Verify installed version and prioritize upgrade for internet-facing brokers.