DEBUGEN

Researchers Bypass RP2350 Secure Debug Lock with Laser Fault Injection and Photon Emission Microscopy

Security researchers have demonstrated a hardware attack that restores Secure Debug access on the RP2350 microcontroller revision A4 despite permanent OTP fuses disabling it. Using photon emission microscopy they first located the exact physical bits of the DEBUGEN register, then applied precisely timed 980 nm laser pulses to flip two critical bits and re-enable the Mem-AP ports. The attack requires decapping the chip from the backside and laboratory equipment costing around $250,000, but succeeds in seconds once calibrated. It bypasses the CRIT1.DEBUG_DISABLE fuse, TrustZone restrictions, and glitch detectors by resetting the device before firmware can re-lock the OTP page. The technique was developed against the updated A4 silicon released after the first Raspberry Pi Hacking Challenge. The work highlights that even heavily hardened microcontrollers remain vulnerable to sophisticated physical attacks when an attacker has direct silicon access.