curl: CVE-2021-22945: UAF and double-free in MQTT sending

Vulnerability Description libcurl version 7.77.0 has a Use-After-Free and a Double-Free in lib/mqtt.c in the function mqttdoing on lines 556 - 563: c ifmq-nsend / send the remainder of an outgoing packet / char ptr = mq-sendleftovers; result = mqttsenddata, mq-sendleftovers, mq-nsend; freeptr;...