A timing side channel was discovered in AT91bootstrap before 3.9.2. It can be exploited by attackers with physical access to forge CMAC values and subsequently boot arbitrary code on an affected system.

AT91bootstrap before 3.9.2 does not properly wipe encryption and authentication keys from memory before passing control to a less privileged software component. This can be exploited to disclose these keys and subsequently encrypt and sign the next boot stage (such as the bootloader).