https://www.bleepingcomputer.com/news/security/u-boots-trusted-boot-validation-bypassed/

Memory handling issues in U-Boot open-source bootloader for embedded devices make possible multiple exploitation techniques that lead to arbitrary code execution.

U-Boot, short for the Universal Boot Loader, is a first-stage and second-stage bootloader. It is responsible for the initial hardware configuration and loading the operating system (OS) kernel.