RaspberryMatic Unauthenticated Remote Code Execution vulnerability through HMServer File Upload

RaspberryMatic is an open-source operating system for HomeMatic internet-of-things devices. RaspberryMatic / OCCU prior to version 3.75.6.20240316 contains a unauthenticated remote code execution (RCE) vulnerability, caused by multiple issues within the Java based `HMIPServer.jar` component. RaspberryMatric includes a Java based `HMIPServer`, that can be accessed through URLs starting with `/pages/jpages`. The `FirmwareController` class does however not perform any session id checks, thus this feature can be accessed without a valid session. Due to this issue, attackers can gain remote code execution as root user, allowing a full system compromise. Version 3.75.6.20240316 contains a patch.