Exploiting Undocumented Hardware Blocks in the LPC55S69 Microcontroller #ReverseEngineering

Oxide Computer was designing a new computer system from the ground up. Along the way they carefully reviewed all hardware selected to ensure it meets functional and security needs. This work includes reverse engineering where necessary to get a full understanding of the hardware. During the process of reverse engineering the NXP LPC55S69 ROM, they discovered an undocumented hardware block intended to allow NXP to fix bugs discovered in the ROM by applying patches from on-device flash as part of the boot process.

Unfortunately, this undocumented block is left open and accessible by non-secure, unprivileged user code thus allowing attackers to make runtime modifications to purportedly trusted APIs, allowing them to potentially hijack future execution and subvert multiple security boundaries. This issue has been assigned CVE-2021-31532.

Read more including POC code in the post.


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