CVE-2025-7029: SMI Handler Privilege Escalation Vulnerability

CVE-2025-7029 Overview

CVE-2025-7029 is a firmware vulnerability affecting Gigabyte UEFI implementations. The flaw resides in the Software System Management Interrupt (SMI) handler triggered by SwSmiInputValue 0xB2. A local attacker with high privileges can control the RBX register, which the handler uses to derive OcHeader and OcData pointers passed into power and thermal configuration logic. Because these buffers are not validated before structured memory writes based on OcSetup NVRAM values, an attacker can corrupt System Management RAM (SMRAM) and escalate to System Management Mode (SMM). SMM sits below the operating system and hypervisor, giving successful exploitation the ability to bypass Secure Boot, kernel protections, and endpoint security.

Critical Impact
Arbitrary SMRAM corruption enables SMM privilege escalation, allowing persistent, OS-invisible firmware implants below the kernel and hypervisor.

Affected Products

Gigabyte UEFI firmware exposing the SwSmiInputValue 0xB2 handler
Motherboards using the vulnerable OcSetup NVRAM-driven power and thermal configuration logic
Systems referenced in Binarly advisory BRLY-DVA-2025-011 and CERT/CC VU#746790

Discovery Timeline

2025-07-11 - CVE-2025-7029 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7029

Vulnerability Analysis

The vulnerability lives in a Software SMI handler dispatched when a value of 0xB2 is written to the SMI command port. When execution enters SMM, the handler reads the RBX general-purpose register from the saved CPU state to compute two pointers, OcHeader and OcData. These pointers feed downstream routines that apply power and thermal settings drawn from the OcSetup NVRAM variable. The handler performs multiple structured writes through the attacker-supplied pointers without validating that they reference memory outside SMRAM or that the target regions are writable. This is a classic SMM callout and unchecked-pointer pattern that allows corruption of SMRAM contents and control-flow structures.

Root Cause

The root cause is missing input validation of attacker-controlled pointers before use in privileged memory writes. The handler trusts register-supplied values as legitimate buffers rather than sanitizing them against the SMRAM boundary and Communication Buffer whitelist. Combined with NVRAM-controlled write content sourced from OcSetup, this yields a write-what-where primitive inside SMM.

Attack Vector

An attacker with administrative privileges on the operating system triggers the SMI by writing 0xB2 to I/O port 0xB2 after loading RBX with a crafted pointer. The handler then performs structured writes to attacker-chosen memory. Because the writes execute inside SMM, they bypass OS, hypervisor, and Secure Boot protections. Successful exploitation can install a persistent SMM implant, disable firmware protections, or tamper with measurements consumed by remote attestation.

No verified public exploit code is available. Refer to the Binarly Security Advisory BRLY-DVA-2025-011 and CERT/CC Vulnerability Note VU#746790 for technical details.

Detection Methods for CVE-2025-7029

Indicators of Compromise

Unexpected writes to I/O port 0xB2 originating from non-vendor tooling or unsigned drivers
Kernel drivers issuing HalSetBusDataByOffset or raw out instructions against the SMI command port
Unexplained changes to the OcSetup UEFI NVRAM variable outside of firmware update windows
Firmware integrity attestation failures reported by trusted platform module (TPM) event logs

Detection Strategies

Baseline legitimate SMI 0xB2 triggers during platform initialization and alert on runtime invocations from user-installed drivers
Monitor for loading of signed but abusable driver primitives that expose port I/O to user mode
Compare firmware measurements against a known-good gold image using platform attestation
Correlate administrative privilege escalations with subsequent kernel driver loads that touch SMI ports

Monitoring Recommendations

Enable UEFI variable auditing where supported and log changes to OcSetup
Ingest firmware and TPM event logs into centralized logging for anomaly hunting
Track driver load events and command-line telemetry for tools known to issue SMI triggers
Review vendor firmware advisories continuously and correlate installed BIOS versions against fixed builds

How to Mitigate CVE-2025-7029

Immediate Actions Required

Apply the latest Gigabyte BIOS/UEFI update for the affected motherboard model as published on the Gigabyte Security Support Page
Restrict local administrative access, since exploitation requires high privileges on the host
Block installation and loading of unsigned or known-abusable kernel drivers that grant raw I/O port access
Verify Secure Boot, BIOS write protection, and SMM protections such as SMM_Code_Chk_En are enabled after updating

Patch Information

Gigabyte has released firmware updates addressing the unvalidated SMI handler. Consult the Gigabyte Security Support Page and the CERT/CC advisory VU#746790 for the list of affected models and corresponding fixed BIOS versions. Firmware updates must be applied per model; there is no runtime software patch for SMM code.

Workarounds

Where a firmware update is not yet available, enforce strict allow-listing of kernel drivers to prevent user-mode triggering of SwSmiInputValue 0xB2
Use Windows Defender Application Control or equivalent Linux driver-signing policies to block vulnerable-driver primitives
Enable hypervisor-protected code integrity (HVCI) and Virtualization-Based Security (VBS) to raise the bar for kernel-level attackers
Physically and logically restrict administrative access to systems running unpatched firmware

bash

# Example: verify current BIOS version on Linux before and after patching
sudo dmidecode -s bios-version
sudo dmidecode -s bios-release-date

# Example: enumerate UEFI variables and inspect OcSetup on Linux
sudo ls /sys/firmware/efi/efivars | grep -i OcSetup