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 process_segment in components/bootloader_support/src/esp_image_format.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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-18558
• https://github.com/espressif/esp-idf/releases
• https://www.espressif.com/en/news/Espressif_Product_Security_Advisory_Concerning_Secure_Boot_(CVE-2018-18558)
• https://www.espressif.com/en/news/Espressif_Product_Security_Advisory_Concerning_Secure_Boot_%28CVE-2018-18558%29