Hydroph0bia Secure Boot bypass in InsydeH2O SecureFlashDxe

Repository is a real exploit/PoC and educational research package for CVE-2025-4275 (Hydroph0bia), a Secure Boot bypass in Insyde H2O firmware caused by NVRAM variable shadowing. The repo is not tied to Metasploit/Nuclei/etc.; it is a standalone collection of EDK2 UEFI drivers/apps, Windows helper tools, Bash scripts, and deployment automation. Structure: (1) '01 Vulnerable Binaries/02 Educational Binary/CVE_2025_4275_Pkg' contains an EDK2 package with three emulation DXE drivers and two UEFI applications. BdsDxe emulator creates volatile SecureFlashCertData/SecureFlashSetupMode variables; SecureFlashDxe emulator loads \EFI\Insyde\isflash.bin via LoadImage; SecurityStubDxe emulator installs an EFI_SECURITY2_ARCH_PROTOCOL handler that performs Authenticode verification but intentionally omits the non-volatile attribute check, reproducing the vulnerable trust decision. The UEFI apps explain the vulnerability and create/clear shadow variables directly in firmware context. (2) '02 Exploitation Flow Analysis/PoC' contains the practical exploit chain: certificate generation script, ESL-to-C conversion script, Windows NVRAM injector, malicious DXE payload source, Windows verification utility, signing script, and deployment batch file that mounts the ESP, copies the signed payload, writes startup.nsh, registers Driver0000, and reboots. (3) Markdown docs explain exploitation flow, impact, and mitigation; '03 Automated Detection Framework' is only a placeholder README. Main exploit capability: local privileged attacker writes SecureFlashCertData and SecureFlashSetupMode under GUID {382AF2BB-FFFF-ABCD-AAEE-CCE099338877} as non-volatile variables before reboot. Because vulnerable SecurityStubDxe does not verify that these variables are volatile, it accepts the attacker certificate as a trust anchor and allows attacker-signed UEFI binaries to load. The PoC then signs a DXE driver, places it on the EFI System Partition, registers it through DriverXXXX or triggers it through \EFI\Insyde\isflash.bin, and demonstrates arbitrary pre-OS execution while Secure Boot appears enabled. Notable endpoints/targets are firmware variable names, the SecureFlash GUID, ESP paths such as \EFI\Insyde\isflash.bin and \EFI\poc\HydrophobiaPoCDxeDriver_signed.efi, and the evidence variable HydrophobiaPoCRan. No C2 or external network infrastructure is present; this is a local/firmware exploit chain rather than a network exploit.

This repository provides a proof-of-concept (PoC) exploit targeting Insyde-based UEFI firmware Secure Flash protections. The structure includes: - A UEFI DXE driver (SecureFlashPoC/SecureFlashPoC.c and SecureFlashPoCDxe.inf) that manipulates NVRAM variables and triggers the Secure Flash process. - A Windows tool (sfcd/sfcd.c) that sets or clears specific NVRAM variables (SecureFlashSetupMode, SecureFlashCertData) using the Windows API, requiring administrative privileges. - Batch and EFI shell scripts (sfpoc/sfpoc.cmd, startup_1.nsh, startup_2.nsh) that automate the process of mounting the EFI System Partition, copying payloads (such as isflash.bin, bios.bin, fpt_signed.efi, sfpoc_signed.efi), replacing EFI bootloaders, and executing the firmware flashing process. The exploit's main capability is to bypass Secure Flash protections by setting crafted NVRAM variables and replacing EFI boot files, allowing arbitrary firmware images to be flashed. This can result in persistent compromise of the system at the firmware level. The attack is local and requires administrative access to the target system. The repository is operational, providing both the code and scripts necessary to perform the attack, but does not include a fully weaponized, automated tool.