CVE-2025-66023Network attack vector

Broker crash via pre-CONNACK packet state confusion

Published Jan 1, 2026 · Updated Jan 1, 2026

Heap use-after-free in the NanoMQ bridge client before 0.24.5 allows remote attackers controlling a bridged broker to crash NanoMQ. The embedded NanoNNG MQTT client processes packets before requiring CONNACK first, creating state confusion that leaves freed heap memory reachable. Exploitation requires NanoMQ to initiate a bridge connection to an attacker-controlled broker, which can interrupt the broker service.

CVSS severity6.9
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap use-after-free in the NanoMQ bridge client before 0.24.5 allows remote attackers controlling a bridged broker to crash NanoMQ. The embedded NanoNNG MQTT client processes packets before requiring CONNACK first, creating state confusion that leaves freed heap memory reachable. Exploitation requires NanoMQ to initiate a bridge connection to an attacker-controlled broker, which can interrupt the broker service.

The record

CVE
CVE-2025-66023
Published
Jan 1, 2026
Updated
Jan 1, 2026
Vendor
EMQ Technologies
Product
NanoMQ
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 1, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.24.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

EMQ Technologies · NanoMQversion=< 0.24.5

Published CVSS scores

6.9GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
4.9NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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