NanoMQ MQTT Broker up to 0.24.4 use after free

Summaryinfo

A vulnerability labeled as critical has been found in NanoMQ MQTT Broker up to 0.24.4. The affected element is an unknown function. Such manipulation leads to use after free. This vulnerability is documented as CVE-2025-66023. The attack can be executed remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in NanoMQ MQTT Broker up to 0.24.4. Affected by this issue is an unknown part. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. Versions prior to 0.24.5 have a Heap-Use-After-Free (UAF) vulnerability within the MQTT bridge client component (implemented via the underlying NanoNNG library). The vulnerability is triggered when NanoMQ acts as a bridge connecting to a remote MQTT broker. A malicious remote broker can trigger a crash (Denial of Service) or potential memory corruption by accepting the connection and immediately sending a malformed packet sequence. Version 0.34.5 contains a patch. The patch enforces stricter protocol adherence in the MQTT client SDK embedded in NanoMQ. Specifically, it ensures that CONNACK is always the first packet processed in the line. This prevents the state confusion that led to the Heap-Use-After-Free (UAF) when a malicious server sent a malformed packet sequence immediately after connection establishment. As a workaround, validate the remote broker before bridging.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2025-66023 since 11/21/2025. The exploitation is known to be difficult. The attack may be launched remotely. The exploitation needs additional levels of successful authentication. There are neither technical details nor an exploit publicly available.

Upgrading to version 0.24.5 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-206141). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• NanoMQ

Name

• MQTT Broker

Version

• 0.24.0
• 0.24.1
• 0.24.2
• 0.24.3
• 0.24.4

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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