The bootloader of the homee Brain Cube V2 through 2.23.0 allows attackers with physical access to gain root access by manipulating the U-Boot environment via the CLI after connecting to the internal UART interface.
https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2019-026.txt
https://store.hom.ee/collections/all/products/homee-brain-cube