An issue was discovered on Renesas SmartBond DA14691, DA14695, DA14697, and DA14699 devices. The Nonce used for on-the-fly decryption of flash images is stored in an unsigned header, allowing its value to be modified without invalidating the signature used for secureboot image verification. Because the encryption engine for on-the-fly decryption uses AES in CTR mode without authentication, an attacker-modified Nonce can result in execution of arbitrary code.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.