As the injection of new codes in equipment that has communication link is a critical process due to the possibility of injection of broke or malicious codes, this document proposes a protocol for the safe injection of code in satellite microcontrollers of the CubeSat’ type. This protocol is based on the use of HMAC with SHA-3 to guarantee integrity and authenticity and is enhanced by the same security measures to mitigate communication link problems and satellite attacks, such as guarantee of delivery and displacement between communication windows and periods of high processing.