CVE-2025-7028: Software SMI Handler Privilege Escalation

CVE-2025-7028 Overview

CVE-2025-7028 is a firmware vulnerability in a Gigabyte UEFI System Management Mode (SMM) module. The Software SMI handler exposed at SwSmiInputValue 0x20 accepts an attacker-controlled FuncBlock pointer through the RBX and RCX registers. The handler dispatches this pointer to flash management routines including ReadFlash, WriteFlash, EraseFlash, and GetFlashInfo without validating that the structure or its BufAddr member lie outside System Management RAM (SMRAM). A local attacker with elevated privileges can gain arbitrary read and write access to SMRAM, corrupt firmware memory, or install persistent implants below the operating system.

Critical Impact
Arbitrary SMRAM read/write from ring 0 enables persistent, OS-invisible firmware implants and Secure Boot bypass on affected Gigabyte systems.

Affected Products

Gigabyte UEFI firmware images containing the vulnerable SMM module (see Gigabyte Security Support)
Systems referenced in Binarly advisory BRLY-DVA-2025-010
Platforms listed in CERT/CC Vulnerability Note VU#746790

Discovery Timeline

2025-07-11 - CVE-2025-7028 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7028

Vulnerability Analysis

The vulnerability resides in a Software SMI (System Management Interrupt) handler registered by a Gigabyte SMM driver. When ring 0 software triggers SMI 0x20, the handler reads the FuncBlock pointer from CPU registers RBX and RCX and passes it directly into flash service dispatch functions. These functions dereference both the outer structure and the nested BufAddr field to perform SPI flash read, write, erase, and info operations.

Because SMM code executes at the highest hardware privilege level (ring -2) with full access to SMRAM and physical memory, an attacker who can trigger the SMI can coerce the handler to read from or write to arbitrary physical addresses. This includes SMRAM itself, which is normally isolated by the SMRR and TSEG protections. The result is a confused-deputy primitive that turns a legitimate flash service into an arbitrary memory read/write oracle.

Root Cause

The root cause is missing input validation on the communication buffer supplied to an SMM handler [CWE-20]. The handler trusts the caller-supplied FuncBlock pointer and its embedded BufAddr field without verifying that the referenced memory ranges are outside SMRAM. Secure SMI handlers must call SmmIsBufferOutsideSmmValid() on every attacker-controllable pointer before dereferencing it.

Attack Vector

Exploitation requires local code execution with kernel or administrator privileges to issue a Software SMI. The attacker populates RBX and RCX with a pointer to a crafted FuncBlock structure whose BufAddr field points into SMRAM, then writes 0x20 to I/O port 0xB2 to trigger the SMI. The vulnerable handler dereferences the structure and performs flash-backed reads or writes against the attacker-chosen address, leaking SMRAM contents or overwriting them. Successful exploitation enables installation of firmware-resident implants that survive operating system reinstallation.

No public proof-of-concept exploit is currently listed for this CVE. Refer to the Binarly advisory BRLY-DVA-2025-010 for structural details of the vulnerable handler.

Detection Methods for CVE-2025-7028

Indicators of Compromise

Unexpected writes to SPI flash regions or unexplained BIOS version changes reported by platform firmware telemetry.
Kernel drivers or userland tools invoking I/O port 0xB2 with value 0x20 outside of vendor firmware update workflows.
SMRAM integrity measurements from TPM PCR 0 or Intel BootGuard logs diverging from a known-good baseline.

Detection Strategies

Compare platform firmware images against vendor-signed baselines using tools such as CHIPSEC or Binarly efiXplorer to identify tampering.
Hunt for user-mode or kernel-mode code that maps physical memory and issues Software SMIs, a behavior atypical for standard applications.
Correlate endpoint telemetry for driver loads granting \Device\PhysicalMemory access with subsequent I/O port 0xB2 writes.

Monitoring Recommendations

Enable and forward UEFI firmware event logs and TPM measured-boot data to a centralized analytics platform for baseline deviation analysis.
Monitor endpoints for the installation of signed but abusable drivers commonly used to invoke SMIs from user space (BYOVD patterns).
Track Gigabyte firmware update advisories and inventory affected motherboards across the fleet.

How to Mitigate CVE-2025-7028

Immediate Actions Required

Inventory Gigabyte-based systems and cross-reference them with the models listed in CERT/CC VU#746790 and Binarly BRLY-DVA-2025-010.
Apply UEFI firmware updates published on the Gigabyte Security Support page once available for each affected model.
Restrict local administrator and kernel-driver-loading privileges to reduce the population of accounts capable of issuing Software SMIs.

Patch Information

Gigabyte publishes BIOS updates that add SMRAM validation to the affected SMI handler through its Security Support portal. Consult the vendor page for the correct firmware version per motherboard SKU. Firmware updates must be applied per platform; there is no operating-system-level patch that fully remediates the issue.

Workarounds

Enforce Secure Boot, Intel BootGuard, and BIOS write protection to raise the cost of persistence even if SMRAM is temporarily corrupted.
Enable hypervisor-based code integrity (HVCI) and driver blocklists to prevent loading of vulnerable third-party drivers used to reach SMM from user space.
Where firmware updates are not yet available, isolate affected systems from workloads that grant untrusted software administrative access.

bash

# Verify installed BIOS version on Windows and Linux before and after patching
# Windows (PowerShell)
Get-CimInstance -ClassName Win32_BIOS | Select-Object Manufacturer, SMBIOSBIOSVersion, ReleaseDate

# Linux
sudo dmidecode -s bios-vendor
sudo dmidecode -s bios-version
sudo dmidecode -s bios-release-date