In Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with topic length = 0.

In Mosquitto before 2.0.16, excessive memory is allocated based on malicious initial packets that are not CONNECT packets.

In Eclipse Mosquitto 1.5.0 to 1.6.5 inclusive, if a malicious MQTT client sends a SUBSCRIBE packet containing a topic that consists of approximately 65400 or more '/' characters, i.e. the topic hierarchy separator, then a stack overflow will occur.

Last updated 26 August 2025

In Eclipse Mosquitto 1.4.15 and earlier, a Memory Leak vulnerability was found within the Mosquitto Broker. Unauthenticated clients can send crafted CONNECT packets which could cause a denial of service in the Mosquitto Broker.

In Mosquitto before 1.4.12, pattern based ACLs can be bypassed by clients that set their username/client id to '#' or '+'. This allows locally or remotely connected clients to access MQTT topics that they do have the rights to. The same issue may be present in third party authentication/access control plugins for Mosquitto.

The Windows Installation component of TIBCO Software Inc.'s TIBCO Messaging - Eclipse Mosquitto Distribution - Core - Community Edition and TIBCO Messaging - Eclipse Mosquitto Distribution - Core - Enterprise Edition contains a vulnerability that theoretically allows a low privileged attacker with local access on some versions of the Windows operating system to insert malicious software. The affected component can be abused to execute the malicious software inserted by the attacker with the elevated privileges of the component. This vulnerability results from a lack of access restrictions on certain files and/or folders in the installation. Affected releases are TIBCO Software Inc.'s TIBCO Messaging - Eclipse Mosquitto Distribution - Core - Community Edition: versions 1.3.0 and below and TIBCO Messaging - Eclipse Mosquitto Distribution - Core - Enterprise Edition: versions 1.3.0 and below.