CVE-2025-66023 NanoMQ has Use-After-Free of malformed bridging message
A malicious remote broker can trigger a use-after-free in NanoMQ's bridge client, causing a crash or potential code execution.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-66023?
CVE-2025-66023 is a medium-severity use after free vulnerability in nanomq, published on 1 Jan 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
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.
Weakness: CWE-416
Which versions are affected by CVE-2025-66023?
It affects 1 product.
Products include Emqx Nanomq.
How do I fix CVE-2025-66023?
No fix has been published for CVE-2025-66023 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-66023 being exploited?
There is no known exploitation of CVE-2025-66023 in the wild and no public exploit code.
Other vulnerabilities in nanomq
Sources
Also known as GHSA-24f7-q5hh-27hf.