CVE-2025-54502: AMD APCB SMM Privilege Escalation Flaw

CVE-2025-54502 Overview

CVE-2025-54502 is a privilege escalation vulnerability affecting the AMD Platform Configuration Blob (APCB) System Management Mode (SMM) driver. The vulnerability stems from incorrect use of boot services within the APCB SMM driver, which could allow a privileged attacker with local access at Ring 0 (kernel level) to escalate privileges and potentially achieve arbitrary code execution.

Critical Impact

This vulnerability allows attackers who already possess kernel-level access to escalate privileges into SMM, one of the most privileged execution contexts in x86 architecture. Successful exploitation could enable arbitrary code execution with SMM privileges, potentially bypassing security mechanisms and persisting beyond operating system reinstallation.

Affected Products

• AMD Platform Configuration Blob (APCB) SMM Driver
• AMD BIOS/UEFI firmware implementations utilizing the vulnerable APCB driver
• Systems with AMD processors running affected firmware versions

Discovery Timeline

• April 16, 2026 - CVE-2025-54502 published to NVD
• April 16, 2026 - Last updated in NVD database

Technical Details for CVE-2025-54502

Vulnerability Analysis

This vulnerability is classified under CWE-668 (Exposure of Resource to Wrong Sphere), which indicates that a resource intended for one execution context is improperly exposed to another. In the context of SMM drivers, this represents a critical security boundary violation.

SMM operates as the most privileged execution mode on x86 systems, running at Ring -2 and having unrestricted access to all system memory and hardware. The APCB driver, responsible for handling platform configuration during boot, incorrectly utilizes boot services in a manner that can be abused by an attacker with Ring 0 (kernel) access.

The attack requires local access and high privileges (kernel-level access) to exploit. However, the complexity of the attack is considered high due to the specialized knowledge required to manipulate SMM operations. If successful, the attacker can achieve complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of CVE-2025-54502 lies in the improper use of UEFI Boot Services within the SMM context. Boot Services are intended to be available only during the boot phase and should be terminated before the operating system takes control. When SMM handlers incorrectly reference or utilize boot service pointers after the ExitBootServices() call, the memory previously occupied by these services can be reclaimed and manipulated by OS-level code.

An attacker with kernel access can allocate memory at the addresses where boot service function pointers were previously stored, placing malicious code at these locations. When the vulnerable SMM handler is triggered and attempts to call the now-invalid boot service, execution is redirected to the attacker-controlled code, which then runs with SMM privileges.

Attack Vector

The attack requires local access with Ring 0 (kernel-level) privileges. The attacker must:

1. Identify the memory addresses previously used by boot services
2. Allocate and control memory at those locations after ExitBootServices() has been called
3. Place malicious shellcode in the controlled memory regions
4. Trigger the vulnerable SMM handler through System Management Interrupt (SMI)
5. The SMM handler attempts to call the stale boot service pointer, executing attacker code with SMM privileges

This type of vulnerability is commonly referred to as a "call-out" vulnerability in SMM security research. The attack enables SMM code execution, which operates outside the visibility of the operating system and most security software, making it extremely valuable for persistent, stealthy attacks.

Detection Methods for CVE-2025-54502

Indicators of Compromise

• Unexpected System Management Interrupt (SMI) activity or anomalous SMI frequency patterns
• Memory allocation attempts targeting known UEFI boot service address ranges
• Firmware integrity check failures or unexpected modifications to BIOS/UEFI components
• Unusual kernel driver loading or memory mapping operations targeting low memory regions

Detection Strategies

• Implement firmware integrity monitoring using platform security features such as AMD Platform Secure Boot
• Deploy endpoint detection solutions capable of monitoring SMI activity and kernel-level operations
• Utilize SentinelOne Singularity Platform for real-time kernel activity monitoring and behavioral analysis
• Establish baseline SMI frequency metrics and alert on significant deviations

Monitoring Recommendations

• Enable AMD Secure Boot and firmware TPM measurements to detect firmware tampering
• Configure logging for kernel-level memory allocation operations, particularly those targeting typical UEFI memory ranges
• Implement periodic firmware version auditing against known vulnerable versions
• Monitor for unauthorized kernel driver installations that could be used as a staging point for this attack

How to Mitigate CVE-2025-54502

Immediate Actions Required

• Review AMD Security Bulletin SB-7054 for specific affected products and remediation guidance
• Identify all systems with AMD processors running potentially vulnerable BIOS/UEFI firmware versions
• Apply firmware updates from your system or motherboard manufacturer as they become available
• Restrict local administrative and kernel-level access to trusted personnel only

Patch Information

AMD has published Security Bulletin SB-7054 addressing this vulnerability. System administrators should consult this bulletin and coordinate with their hardware vendors (OEMs) to obtain updated BIOS/UEFI firmware that addresses the incorrect boot service usage in the APCB SMM driver.

Firmware updates must be applied through your specific hardware manufacturer's update process, as AMD provides mitigation guidance to OEMs who then distribute platform-specific updates.

Workarounds

• Restrict physical access to affected systems to reduce the risk of local exploitation
• Implement strict controls on kernel-mode driver loading using application control policies
• Enable Secure Boot to help prevent unauthorized firmware modifications
• Deploy SentinelOne agents to monitor and protect against kernel-level threats that could be used as prerequisites for this attack

# Example: Verify AMD Secure Boot status (system-dependent)
# Check BIOS/UEFI settings for Platform Secure Boot configuration
# Consult your system vendor documentation for specific commands

# Example: Query firmware version on Linux systems
sudo dmidecode -t bios | grep -E "Vendor|Version|Release"

# Review AMD security bulletin for your specific platform
# https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-7054.html