CVE-2026-5857 Contiki-NG MQTT Client Out-of-Bounds Write in PUBLISH Topic Parser via Persistent State Between TCP Segments

Contiki-NG's MQTT client parsepublishvhdr in os/net/app-layer/mqtt/mqtt.c sets topiclenreceived=1 before checking topiclen against the 64-byte limit, so an over-length topic returns early but leaves the flag set. On the next TCP segment, tcpinput re-invokes the parser with topicreceived==0, and t...