In this physical attack, an attacker may potentially exploit the Zynq-7000 SoC First Stage Boot Loader (FSBL) by bypassing authentication and loading a malicious image onto the device. This in turn may further allow the attacker to perform additional attacks such as such as using the device as a decryption oracle. An anticipated mitigation via a 2022.1 patch will resolve the issue.

On Xilinx Zynq-7000 SoC devices, physical modification of an SD boot image allows for a buffer overflow attack in the ROM. 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 a way that causes a buffer overflow in the ROM.

When booting a Zync-7000 SOC device from nand flash memory, the nand driver in the ROM does not validate the inputs when reading in any parameters in the nand’s parameter page. IF a field read in from the parameter page is too large, this causes a buffer overflow that could lead to arbitrary code execution. Physical access and modification of the board assembly on which the Zynq-7000 SoC device mounted is needed to replace the original NAND flash memory with a NAND flash emulation device for this attack to be successful.