CVE-2025-22850: Intel UEFI Race Condition Vulnerability

CVE-2025-22850 Overview

CVE-2025-22850 is a Time-of-check Time-of-use (TOCTOU) race condition vulnerability discovered in the UEFI PdaSmm module for some Intel reference platforms. This vulnerability allows a privileged local attacker to potentially disclose sensitive information through exploitation of a timing window between security validation and resource access.

Critical Impact

A privileged local attacker exploiting this race condition can achieve unauthorized information disclosure from the UEFI System Management Mode (SMM), potentially exposing sensitive platform data and firmware secrets.

Affected Products

• Intel Reference Platform UEFI Firmware with PdaSmm Module
• Systems based on affected Intel reference platform designs
• OEM implementations using vulnerable Intel UEFI reference code

Discovery Timeline

• 2026-03-10 - CVE-2025-22850 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2025-22850

Vulnerability Analysis

This vulnerability is classified as CWE-367 (Time-of-check Time-of-use Race Condition). The flaw exists in the UEFI PdaSmm module, which operates within System Management Mode—a highly privileged execution environment in x86 processors. The vulnerability occurs when there is a timing gap between when a security check is performed on a resource and when that resource is actually used.

In SMM handlers, TOCTOU vulnerabilities are particularly dangerous because SMM operates at a higher privilege level than the operating system. The attack requires local access with high privileges (such as kernel-level or administrator access) and involves high attack complexity. While no user interaction is required, the attacker must carefully time their exploitation to hit the race window between the security validation and the actual data access.

The vulnerability impacts confidentiality with high severity but does not affect system integrity or availability. This suggests the attacker can read sensitive data but cannot modify system state or cause denial of service through this specific flaw.

Root Cause

The root cause lies in the improper synchronization within the PdaSmm module's security validation logic. When the SMM handler processes requests, it performs a security check on input parameters or memory regions at one point in time, but by the time it actually uses those values, an attacker with sufficient privileges may have modified them. This creates a window of opportunity where the checked value differs from the used value, bypassing the intended security controls.

TOCTOU vulnerabilities in SMM code typically arise from:

• Non-atomic validation and use of shared memory buffers
• Improper handling of communication buffers between runtime and SMM contexts
• Missing locks or memory barriers around critical sections

Attack Vector

The attack vector is local, requiring the adversary to have an existing privileged foothold on the target system. The attacker must be able to execute code with elevated privileges (kernel mode or equivalent) to manipulate memory regions that the SMM handler validates.

The exploitation technique involves:

1. Triggering the SMM handler through a Software Management Interrupt (SMI)
2. Racing to modify the validated data between the check and use operations
3. Winning the race condition to cause the SMM handler to process attacker-controlled data
4. Leveraging the resulting information disclosure to extract sensitive firmware or platform data

Due to the high complexity nature of this attack, reliable exploitation requires precise timing and potentially multiple attempts. The absence of attack requirements (AT:N) indicates that once the prerequisites are met, no additional conditions need to be satisfied.

Detection Methods for CVE-2025-22850

Indicators of Compromise

• Unusual frequency of Software Management Interrupts (SMI) being triggered on the system
• Anomalous memory access patterns in regions adjacent to SMM communication buffers
• Evidence of timing-based attacks or rapid repeated operations targeting UEFI interfaces

Detection Strategies

• Monitor for suspicious SMI activity through hardware performance counters or specialized firmware security tools
• Deploy endpoint detection solutions capable of identifying privileged code attempting to interact with SMM interfaces
• Implement firmware integrity monitoring to detect any unauthorized modifications to UEFI components
• Use SentinelOne Singularity Platform to detect malicious kernel-mode activity that may precede SMM exploitation attempts

Monitoring Recommendations

• Enable verbose logging for UEFI and firmware-related events where supported
• Implement continuous firmware integrity verification using measured boot and attestation mechanisms
• Monitor for privilege escalation attempts that could provide the attacker the necessary access level for exploitation

How to Mitigate CVE-2025-22850

Immediate Actions Required

• Review the Intel Security Advisory for specific guidance and affected product details
• Contact your system OEM vendor for firmware updates that address this vulnerability
• Restrict local privileged access to critical systems to reduce the attack surface
• Implement defense-in-depth strategies including Secure Boot and firmware write protection

Patch Information

Intel has published guidance in their security advisory. System administrators should check with their specific OEM vendors for BIOS/UEFI firmware updates that incorporate the fix for the PdaSmm module vulnerability. Firmware updates typically require system restart and should be tested in non-production environments before widespread deployment.

Workarounds

• Limit local administrator and kernel-mode access to trusted personnel and processes only
• Enable hardware-based firmware protections such as BIOS write protection and SPI flash locking where available
• Implement strict access controls and monitoring on systems containing sensitive data
• Consider enabling Intel Boot Guard or similar platform integrity features to prevent unauthorized firmware modifications

Note: As this is a firmware-level vulnerability, applying vendor-provided firmware updates is the definitive remediation. Workarounds can reduce exposure but do not fully address the underlying vulnerability.