CVE-2025-20105: Intel UEFI Firmware Privilege Escalation

CVE-2025-20105 Overview

CVE-2025-20105 is a BIOS/UEFI vulnerability affecting the System Management Mode (SMM) module in Intel reference platform UEFI firmware. The vulnerability stems from improper input validation within the SMM handler, which operates at a higher privilege level than the operating system. A privileged local attacker can exploit this flaw to escalate privileges and achieve code execution within the highly trusted SMM environment.

Critical Impact

Successful exploitation allows attackers with local administrative access to execute arbitrary code in System Management Mode, bypassing operating system security controls and potentially compromising the entire system's integrity at the firmware level.

Affected Products

• Intel Reference Platform UEFI Firmware with vulnerable SMM modules
• Systems utilizing affected Intel reference BIOS implementations
• OEM systems derived from vulnerable Intel reference platforms

Discovery Timeline

• 2026-03-10 - CVE-2025-20105 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2025-20105

Vulnerability Analysis

This vulnerability (CWE-20: Improper Input Validation) exists within the System Management Mode (SMM) handler of Intel's reference platform UEFI firmware. SMM is a specialized operating mode that executes with the highest privilege level on x86 systems, operating independently of the operating system and hypervisors. When triggered via a System Management Interrupt (SMI), the processor transitions to SMM and executes code from System Management RAM (SMRAM), a protected memory region.

The vulnerable SMM module fails to properly validate input parameters passed from less privileged execution contexts. An attacker with privileged local access (such as kernel-level or ring 0 access) can craft malicious SMI handler calls with specially crafted parameters that bypass validation checks. This allows the attacker to influence SMM execution flow and achieve code execution within the SMM context.

The impact extends beyond the immediate system, as noted in the CVSS assessment showing high subsequent system impact across confidentiality, integrity, and availability. SMM-level compromise can enable persistent firmware implants, secure boot bypass, and other attacks that survive operating system reinstallation.

Root Cause

The root cause is insufficient input validation in the SMM handler code. When processing parameters from SMI calls, the firmware fails to adequately verify that supplied values fall within expected bounds or meet required constraints. This oversight allows attackers to inject malicious data that the SMM handler processes as legitimate input, leading to unintended code paths and potential arbitrary code execution.

Attack Vector

The attack requires local access to the target system and elevated privileges (administrative or kernel-level access). The attacker must:

1. Gain privileged local access to the target system
2. Identify the vulnerable SMI handler and its expected parameters
3. Trigger an SMI with crafted malicious parameters
4. Exploit the improper validation to achieve SMM code execution

The attack complexity is low once the prerequisites are met, and no user interaction is required. However, specific attack requirements must be present for successful exploitation.

The vulnerability is exploited through crafted System Management Interrupt calls where input parameters are not properly validated before being processed by the SMM handler. The attacker leverages the implicit trust the SMM handler places in incoming data from higher-ring code to inject malicious values that redirect execution flow or corrupt SMM memory structures. For detailed technical information, refer to the Intel Security Advisory SA-01234.

Detection Methods for CVE-2025-20105

Indicators of Compromise

• Unexpected SMI activity patterns or frequency anomalies detected by firmware monitoring tools
• Modifications to SMRAM regions or SMM handler code signatures
• Unexplained changes to firmware variables or secure boot configuration
• Presence of unauthorized firmware modules or driver loading attempts

Detection Strategies

• Deploy firmware integrity monitoring solutions that validate SMM handler code against known-good baselines
• Monitor system event logs for unusual SMI triggering patterns from user-space or kernel drivers
• Implement hardware-based attestation (Intel TXT or similar) to detect SMM tampering
• Use endpoint detection solutions capable of monitoring for privilege escalation attempts targeting firmware

Monitoring Recommendations

• Enable and review UEFI Secure Boot violation logs regularly
• Configure alerts for firmware update attempts from unauthorized sources
• Monitor for installation of unsigned kernel drivers that could facilitate SMI manipulation
• Track administrative access patterns to systems containing sensitive data

How to Mitigate CVE-2025-20105

Immediate Actions Required

• Review and apply firmware updates from your system OEM that incorporate Intel's patches
• Restrict local administrative access to affected systems to trusted personnel only
• Enable UEFI Secure Boot and ensure it is properly configured
• Monitor affected systems for signs of compromise until patching is complete

Patch Information

Intel has released updated firmware addressing this vulnerability. System administrators should contact their OEM vendors for updated BIOS/UEFI firmware packages that incorporate the fix. Refer to the Intel Security Advisory SA-01234 for detailed patch information and affected product listings.

Workarounds

• Implement strict access controls to limit which users can obtain administrative or kernel-level access
• Enable and configure platform-specific firmware protection features where available
• Deploy application allowlisting to prevent unauthorized code from running with elevated privileges
• Consider network isolation for critical systems until firmware updates can be applied

# Verify Secure Boot status on Linux systems
mokutil --sb-state

# Check current firmware version (Linux)
dmidecode -t bios | grep -E "Version|Release Date"

# Windows: Check firmware version via PowerShell
Get-WmiObject -Class Win32_BIOS | Select-Object SMBIOSBIOSVersion, ReleaseDate