CVE-2018-18558: Input Validation

An issue was discovered in Espressif ESP-IDF 2.x and 3.x before 3.0.6 and 3.1.x before 3.1.1. Insufficient validation of input data in the 2nd stage bootloader allows a physically proximate attacker to bypass secure boot checks and execute arbitrary code, by crafting an application binary that overwrites a bootloader code segment in processsegment in components/bootloadersupport/src/espimageformat.c. The attack is effective when the flash encryption feature is not enabled, or if the attacker finds a different vulnerability that allows them to write this binary to flash memory.