MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

LiamBindle MQTT-C versions prior to 1.1.7 contain a heap-based out-of-bounds read and integer underflow in the mqtt_unpack_publish_response() function in src/mqtt.c. A remote unauthenticated attacker controlling an MQTT broker, or capable of injecting MQTT traffic into an unencrypted session, can crash a subscribed MQTT-C client and potentially disclose adjacent heap memory by sending a single crafted PUBLISH packet.