CVE-2026-40046Network attack vector

Unexpected broker behavior via MQTT length overflow

Published Apr 9, 2026 · Updated Apr 9, 2026

Integer overflow in Apache ActiveMQ 6.0.0 through 6.2.3 allows remote authenticated users to trigger unexpected behavior via MQTT. The MQTT frame decoder accepts a Remaining Length encoding beyond the four-byte protocol maximum, overflows the computed total, and treats one payload as multiple control packets. An established authenticated connection and an enabled MQTT transport connector are required; Apache has not specified effects beyond incorrect packet interpretation and unexpected behavior.

CVSS severity7.5
High
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Apache ActiveMQ 6.0.0 through 6.2.3 allows remote authenticated users to trigger unexpected behavior via MQTT. The MQTT frame decoder accepts a Remaining Length encoding beyond the four-byte protocol maximum, overflows the computed total, and treats one payload as multiple control packets. An established authenticated connection and an enabled MQTT transport connector are required; Apache has not specified effects beyond incorrect packet interpretation and unexpected behavior.

The record

CVE
CVE-2026-40046
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
The Apache Software Foundation
Product
Apache ActiveMQ MQTT
Classifications
CWE-190, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=6.0.0 <6.2.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Apache Software Foundation · Apache ActiveMQ MQTTversion=6.0.0 <6.2.4
The Apache Software Foundation · Apache ActiveMQ Allversion=6.0.0 <6.2.4
The Apache Software Foundation · Apache ActiveMQversion=6.0.0 <6.2.4

Published CVSS scores

5.4GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1190Exploit Public-Facing Application

Public exploit references

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Technologies

Your stack

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Your stack

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