The firmware upgrade function in the admin web interface of the Rittal IoT Interface & CMC III Processing Unit devices checks if the patch files are signed before executing the containing run.sh script. The signing process is kind of an HMAC with a long string as key which is hard-coded in the firmware and is freely available for download. This allows crafting malicious "signed" .patch files in order to compromise the device and execute arbitrary code.

The firmware upgrade function in the admin web interface of the Rittal IoT Interface & CMC III Processing Unit devices checks if the patch files are signed before executing the containing run.sh script. The signing process is kind of an HMAC with a long string as key which is hard-coded in the firmware and is freely available for download. This allows crafting malicious "signed" .patch files in order to compromise the device and execute arbitrary code.