Denial-of-Service Vulnerability in NanoMQ MQTT Broker

CVE-2026-32134

What is CVE-2026-32134?

In versions 0.24.10 and earlier of the NanoMQ MQTT Broker, a vulnerability arises when handling high-concurrency reconnect traffic with a reconnect-collision payload. This flaw can lead to a remote unauthenticated Denial-of-Service condition due to a NULL pointer dereference during MQTT session resumption for clients with clean_start=0. Specifically, during the session restoration process, the broker attempts to copy session metadata from a previously cached connection pipe to a new one without validating whether the pointer is valid. If a reconnection event occurs and the connection information is freed prior to the session restore, it may cause the broker to crash, resulting in service downtime. This issue is resolved in NanoMQ MQTT Broker version 0.24.11.

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