Meshtastic is an open source, off-grid, decentralized, mesh network. Meshtastic uses MQTT to communicate over an internet connection to a shared or private MQTT Server. Nodes can communicate directly via an internet connection or proxied through a connected phone (i.e., via bluetooth). Prior to version 2.5.1, multiple weaknesses in the MQTT implementation allow for authentication and authorization bypasses resulting in unauthorized control of MQTT-connected nodes. Version 2.5.1 contains a patch.
Meshtastic device firmware is a firmware for meshtastic devices to run an open source, off-grid, decentralized, mesh network built to run on affordable, low-power devices. Meshtastic device firmware is subject to a denial of serivce vulnerability in MQTT handling, fixed in version 2.4.1 of the Meshtastic firmware and on the Meshtastic public MQTT Broker. It's strongly suggested that all users of Meshtastic, particularly those that connect to a privately hosted MQTT server, update to this or a more recent stable version right away. There are no known workarounds for this vulnerability.