This Design Advisory describes an attack where a buffer overflow in the SD memory driver is exploited to allow execution of the attacker’s code.
Because the Zynq-7000's boot image header is unencrypted and unauthenticated before use, an attacker can modify the boot header stored on an SD card so that a secure image appears to be unencrypted and they will be able to modify the full range of register initialization values.
Normally, these registers will be restricted when booting securely. Of importance to this attack are two registers that control the SD card’s transfer type and transfer size. These registers could be modified in such a way that causes a buffer overflow in the ROM.
Figure 1 is a high-level summary that can be used to determine whether an existing system is impacted.