In /usr/local/etc/config/addons/mh/loopupd.sh on eQ-3 AG HomeMatic CCU2 2.29.22 devices, software update packages are downloaded via the HTTP protocol, which does not provide any cryptographic protection of the downloaded contents. An attacker with a privileged network position (which could be obtained via DNS spoofing of www.meine-homematic.de or other approaches) can exploit this issue in order to provide arbitrary malicious firmware updates to the CCU2. This can result in a full system compromise.