CVE-2020-8670: Intel BIOS Privilege Escalation Flaw

CVE-2020-8670 Overview

CVE-2020-8670 is a race condition vulnerability affecting the firmware of numerous Intel processors. This firmware-level flaw can allow a privileged user with local access to potentially escalate privileges on affected systems. The vulnerability exists in the BIOS firmware implementation, where improper synchronization of concurrent operations creates a time-of-check to time-of-use (TOCTOU) condition that can be exploited.

This vulnerability is particularly concerning because it affects a broad range of Intel processor families, including consumer-grade Core processors (6th through 11th generation), workstation-class Xeon processors, and processors integrated into industrial control systems from vendors such as Siemens and NetApp.

Critical Impact

A privileged attacker with local access can exploit the race condition in Intel processor firmware to escalate privileges, potentially gaining higher-level system control including access to sensitive data and system configurations.

Affected Products

• Intel Core i3, i5, i7, and i9 processors (6th through 11th generation)
• Intel Xeon Bronze, Silver, Gold, and Platinum processor families
• Intel Xeon D, E, E3, E5, E7, and W processor series
• Siemens SIMATIC Field PG M6, IPC427E, IPC477E, IPC527G, IPC547G, IPC627E, IPC647E, IPC677E, IPC847E, ITP1000
• NetApp AFF, FAS, HCI Compute Node, HCI Storage Node, SolidFire BIOS
• NetApp Cloud Backup

Discovery Timeline

• June 9, 2021 - CVE-2020-8670 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-8670

Vulnerability Analysis

This vulnerability is classified as a race condition (CWE-362), which occurs when the behavior of firmware depends on the sequence or timing of events that are not properly synchronized. In the context of Intel processor firmware, this race condition manifests during operations where the firmware checks a condition and then performs an action based on that condition, but the state can change between the check and the action.

The local attack vector means an attacker must have existing access to the system to exploit this vulnerability. However, the potential impact is significant: successful exploitation could allow a privileged user to gain elevated privileges beyond their current authorization level, potentially compromising confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause is improper synchronization within the Intel BIOS firmware when handling concurrent operations. The firmware fails to properly implement atomic operations or locking mechanisms for certain critical sections, creating a window of opportunity where an attacker can manipulate the system state between a security check and the subsequent privileged operation.

This type of vulnerability, often referred to as Time-of-Check Time-of-Use (TOCTOU), is particularly dangerous in firmware contexts because the exploitation occurs at a privileged level below the operating system, making detection and prevention more challenging.

Attack Vector

An attacker with local, privileged access to an affected system can exploit this vulnerability by timing their malicious operations to coincide with the vulnerable window in the firmware's execution flow. The attack requires:

1. Local access to the affected system
2. Elevated privileges on the system
3. The ability to precisely time operations to exploit the race window
4. Knowledge of the specific firmware operations that are vulnerable

The race condition can be triggered by manipulating system state during firmware operations, allowing the attacker to bypass security checks or execute operations with elevated privileges. While the attack complexity is considered high due to the timing requirements, successful exploitation results in complete compromise of confidentiality, integrity, and availability at the firmware level.

Detection Methods for CVE-2020-8670

Indicators of Compromise

• Unexpected BIOS/UEFI configuration changes without administrative action
• Anomalous system behavior during boot sequences or firmware operations
• Unusual privilege escalation events on systems with affected Intel processors
• Firmware integrity check failures or mismatches

Detection Strategies

• Implement firmware integrity monitoring using TPM-based attestation to detect unauthorized firmware modifications
• Deploy endpoint detection solutions capable of monitoring low-level system calls and firmware interactions
• Enable Secure Boot and monitor for integrity violations or bypass attempts
• Review system logs for unusual privileged operations that coincide with firmware activity

Monitoring Recommendations

• Establish baseline firmware configurations and monitor for deviations using hardware security modules
• Implement continuous monitoring of BIOS/UEFI settings through centralized management solutions
• Configure alerting for any unauthorized firmware update attempts or configuration changes
• Deploy SentinelOne agents with firmware monitoring capabilities to detect exploitation attempts

How to Mitigate CVE-2020-8670

Immediate Actions Required

• Inventory all systems with affected Intel processors and prioritize patching based on exposure
• Apply the latest BIOS/UEFI firmware updates from your system or motherboard manufacturer
• Implement strict access controls to limit local privileged access on affected systems
• Enable Secure Boot and configure BIOS passwords to prevent unauthorized firmware modifications

Patch Information

Intel has released firmware updates to address this vulnerability as documented in Intel Security Advisory SA-00463. Organizations should obtain BIOS/firmware updates from their system vendors:

• Intel systems: Check Intel Security Advisory SA-00463 for guidance
• Siemens industrial systems: Refer to Siemens Security Advisory SSA-309571 for applicable firmware updates
• NetApp systems: See NetApp Security Advisory NTAP-20210702-0002 for patching instructions

Firmware updates should be applied during planned maintenance windows and validated using vendor-provided verification tools.

Workarounds

• Restrict local privileged access to affected systems to only essential personnel
• Implement physical security controls to prevent unauthorized local access
• Enable BIOS/UEFI passwords and disable unnecessary boot options
• Deploy additional monitoring and logging on affected systems until patches can be applied
• Consider network segmentation for systems that cannot be immediately patched

# Example: Verify current BIOS version on Linux systems
dmidecode -s bios-version
dmidecode -s bios-release-date

# Check Intel processor model to verify if affected
cat /proc/cpuinfo | grep -E "model name|microcode"

# Verify Secure Boot status
mokutil --sb-state