Bypassing Memory Protection: Exploiting the FPB in Embedded Systems

The article discusses a newly discovered vulnerability in Cortex-M processors, which are commonly used in embedded devices. The vulnerability is found in the Flash Patch and Breakpoint (FPB) unit, which is intended for debugging and on-the-fly patching of firmware. The FPB can be exploited to bypass memory protection and leak data from an embedded device.
To understand how this works, imagine a superhero with a special power to modify the instructions being executed by the CPU. With this ability, the superhero can bypass security mechanisms that protect the device’s memory. Similarly, the FPB unit can be used to replace instructions and data fetches performed by the CPU, allowing an attacker to modify the behavior of the device.
The article demonstrates how the FPB unit can be exploited to bypass memory protection and leak sensitive information from an embedded device. The authors also discuss how this vulnerability can be used to deploy different attacks against defense mechanisms.
In summary, the FPB unit is a powerful tool for debugging and on-the-fly patching of firmware, but it can also be exploited to bypass memory protection and leak sensitive information from embedded devices. This vulnerability affects many Cortex-M processors used in billions of devices worldwide, highlighting the need for better security measures to protect these devices.