CVE-2025-7027: UEFI SMM Privilege Escalation Vulnerability

CVE-2025-7027 Overview

CVE-2025-7027 is a firmware vulnerability affecting Gigabyte UEFI implementations. The flaw resides in a Software System Management Interrupt (SMI) handler triggered through SwSmiInputValue 0xB2. A local attacker with high privileges can control both the read and write addresses used by the CommandRcx1 function, enabling arbitrary writes into System Management RAM (SMRAM). Successful exploitation results in System Management Mode (SMM) privilege escalation and firmware-level compromise, giving attackers execution below the operating system. The issue was disclosed through Binarly Security Advisory BRLY-2025-009 and CERT Vulnerability Note #746790.

Critical Impact
Arbitrary write into SMRAM enables SMM code execution, bypassing OS-level protections and persisting below the kernel.

Affected Products

Gigabyte UEFI firmware images containing the vulnerable Software SMI handler
Systems exposing the SwSmiInputValue 0xB2 interface with the CommandRcx1 function
Platforms relying on the unvalidated SetupXtuBufferAddress UEFI NVRAM variable

Discovery Timeline

2025-07-11 - CVE-2025-7027 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7027

Vulnerability Analysis

The vulnerability is a firmware-level arbitrary write flaw in a Software SMI handler. When software triggers SMI 0xB2, the handler dispatches to CommandRcx1, which performs a memory copy without validating either endpoint of the operation. The destination address is derived from the SetupXtuBufferAddress UEFI NVRAM variable, which is attacker-influenced and unvalidated. The source address is taken from a pointer read out of the RBX register, also attacker-controlled at SMI entry. Because SMM executes with the highest processor privilege and unrestricted access to physical memory, arbitrary writes into SMRAM allow the attacker to modify SMM handlers or hijack SMM control flow. This produces a firmware compromise that persists across operating system reinstallation and evades traditional endpoint controls.

Root Cause

The root cause is missing input validation on two attacker-controlled pointers consumed inside a privileged SMM handler. Neither the NVRAM-sourced destination nor the register-sourced pointer is bounds-checked against non-SMRAM regions before dereference.

Attack Vector

A local attacker with administrative privileges triggers SwSmi 0xB2 after setting SetupXtuBufferAddress and staging a controlled pointer in RBX. The handler then writes attacker-supplied content into an attacker-chosen SMRAM address, yielding SMM code execution. See the Binarly Security Advisory BRLY-2025-009 and CERT Vulnerability Note #746790 for the technical breakdown.

Detection Methods for CVE-2025-7027

Indicators of Compromise

Unexpected modifications to the SetupXtuBufferAddress UEFI NVRAM variable outside of firmware setup workflows.
Userland processes issuing out 0xB2 instructions or invoking SMI gate drivers from non-vendor tooling.
Firmware measurement mismatches in TPM PCR values after reboot, indicating SMRAM or SMM handler tampering.

Detection Strategies

Baseline the platform's UEFI variables and alert on writes to SetupXtuBufferAddress by non-authorized processes.
Monitor for kernel drivers that expose SMI trigger primitives being loaded on production endpoints.
Use firmware integrity tools such as CHIPSEC to verify SMRAM lockdown and SMI handler integrity.

Monitoring Recommendations

Ingest firmware and UEFI variable telemetry into a centralized data lake for cross-host correlation.
Track privileged local process activity that precedes reboots, since SMM implants often finalize on reset.
Correlate driver-load events with subsequent NVRAM writes to identify pre-exploitation staging.

How to Mitigate CVE-2025-7027

Immediate Actions Required

Inventory Gigabyte-based systems and identify firmware versions exposed to the vulnerable handler.
Apply the vendor firmware update once published on the Gigabyte Security Support Page.
Restrict local administrative access to reduce the population of principals able to invoke SMI 0xB2.

Patch Information

Gigabyte is coordinating fixes through its security response process. Consult the Gigabyte Security Support Page and CERT Vulnerability Note #746790 for the current list of patched firmware images and affected models.

Workarounds

Enforce Secure Boot and BIOS administrator passwords to raise the bar for firmware modification.
Disable or restrict access to XTU-style tuning utilities and drivers that reach the vulnerable SMI handler.
Enable firmware integrity attestation and reject devices whose measurements diverge from a known-good baseline.

bash

# Example: verify SMRAM lockdown and SMI handler integrity with CHIPSEC
sudo chipsec_main -m common.smm
sudo chipsec_main -m common.smrr
sudo chipsec_main -m common.bios_wp