Gigabyte UEFI Vulnerabilities Enables Arbitrary Code Execution in SMM

A critical security disclosure has revealed multiple System Management Mode (SMM) callout vulnerabilities in Gigabyte UEFI firmware modules, potentially allowing attackers to execute arbitrary code in one of the most privileged processor environments.

The vulnerabilities, publicly disclosed on July 11, 2025, through Vulnerability Note VU#746790, affect the highly sensitive SMM environment that operates below the operating system level, making detection and mitigation particularly challenging for traditional security tools.

The discovered vulnerabilities target the Unified Extensible Firmware Interface (UEFI) specification’s interaction with System Management Mode, a highly privileged CPU mode designed for handling low-level system operations.

SMM operates within a protected memory region called System Management RAM (SMRAM) and is accessed exclusively through System Management Interrupt (SMI) handlers, which serve as gateways processing data from specific communication buffers.

The security flaws stem from improper validation of these communication buffers and untrusted pointers from CPU save state registers, creating pathways for SMRAM corruption and unauthorized SMM execution.

Attackers can exploit these vulnerabilities to gain control during early boot phases, recovery modes, or before the operating system fully loads, effectively operating at Ring -2 privilege level—below even the operating system kernel.

What makes these vulnerabilities particularly concerning is their ability to disable critical UEFI security mechanisms, including Secure Boot and Intel BootGuard.

This capability enables attackers to install stealthy firmware implants that maintain persistent control over compromised systems, operating beneath traditional endpoint protection tools’ detection capabilities.

Gigabyte UEFI Vulnerabilities

The disclosure identifies four specific Common Vulnerabilities and Exposures (CVE) entries, each targeting different aspects of the SMM environment.

CVE-2025-7029 involves unchecked use of the RBX register, allowing attackers to control OcHeader and OcData pointers in power and thermal configuration logic, resulting in arbitrary SMRAM writes.

CVE-2025-7028 exploits the lack of validation in function pointer structures derived from RBX and RCX registers, enabling attacker control over critical flash operations through FuncBlock, affecting ReadFlash, WriteFlash, EraseFlash, and GetFlashInfo functions.

CVE-2025-7027 presents a double pointer dereference vulnerability involving memory write locations from unvalidated NVRAM Variable SetupXtuBufferAddress, combined with attacker-controlled content from RBX register pointers.

The final vulnerability, CVE-2025-7026, allows attackers to use the RBX register as an unchecked pointer within the CommandRcx0 function, enabling writes to attacker-specified SMRAM memory locations.

These vulnerabilities collectively provide multiple attack vectors for gaining SMM-level access and control.

Firmware Updates

According to the disclosure, American Megatrends Incorporated (AMI), the original firmware supplier, had previously addressed these vulnerabilities through private disclosures.

However, the vulnerable implementations persisted in Gigabyte’s firmware builds, necessitating this public disclosure by the Binarly Research team.

Gigabyte has responded by issuing updated firmware to address the identified vulnerabilities, with users strongly advised to visit the Gigabyte support website to determine system impact and apply necessary updates.

The vendor response varies significantly across the industry, with AMI, ASUSTeK, Insyde Software, and Intel marked as “Not Affected,” while Gigabyte’s status remains “Unknown” alongside other major vendors including Acer, Amazon, Dell, and Fujitsu.

The disclosure emphasizes that these vulnerabilities may affect firmware supplied through the supply chain, potentially impacting other PC OEM vendors beyond Gigabyte.

Users are advised to monitor vendor information sections for updates as additional manufacturers assess their firmware implementations.

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