In Eclipse Mosquitto, from version 1.3.2 through 2.0.18, if a malicious broker sends a crafted SUBACK packet with no reason codes, a client using libmosquitto may make out of bounds memory access when acting in its onsubscribe callback. This affects the mosquittosub and mosquittorr clients.
The broker in Eclipse Mosquitto 1.3.2 through 2.x before 2.0.16 has a memory leak that can be abused remotely when a client sends many QoS 2 messages with duplicate message IDs, and fails to respond to PUBREC commands. This occurs because of mishandling of EAGAIN from the libc send function.