CVE-2023-25756: Intel Atom X6200fe Firmware Privilege Escalation

CVE-2023-25756 Overview

CVE-2023-25756 is an out-of-bounds read vulnerability in the BIOS firmware for certain Intel processors. This firmware-level security flaw allows an authenticated user with adjacent network access to potentially escalate their privileges on affected systems. The vulnerability exists within the BIOS firmware code and can be exploited by attackers who have already gained initial authentication to the system.

Critical Impact

This vulnerability enables privilege escalation through adjacent network access, potentially allowing authenticated attackers to gain elevated system privileges and compromise the confidentiality, integrity, and availability of affected Intel-based systems.

Affected Products

• Intel Atom X6200FE, X6211E, X6212RE, X6413E, X6414RE, X6425E, X6425RE, X6427FE Processors and Firmware
• Intel Celeron Processor Series (multiple generations including B, G, J, N series)
• Intel Core i3, i5, i7, i9 Processor Series (8th through 13th Generation)
• Intel Pentium Gold Processor Series
• Intel Pentium J6425 and N6415 Processors

Discovery Timeline

• November 14, 2023 - CVE-2023-25756 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-25756

Vulnerability Analysis

This out-of-bounds read vulnerability (CWE-125) resides in the BIOS firmware layer of numerous Intel processor families. The flaw occurs when the BIOS firmware improperly handles memory boundaries during certain operations, allowing read access beyond the intended buffer limits. An attacker who has already authenticated to the system and has adjacent network access can leverage this vulnerability to read sensitive memory contents that should be protected.

The vulnerability is particularly concerning because it exists at the firmware level, which operates below the operating system and is therefore difficult to detect and remediate through traditional software-based security controls. BIOS/UEFI vulnerabilities can persist across operating system reinstallations and may survive typical incident response procedures.

Successful exploitation requires the attacker to be authenticated and have adjacent network access (such as being on the same local network segment). Once exploited, the vulnerability can lead to privilege escalation, potentially granting the attacker elevated access to system resources and sensitive data.

Root Cause

The root cause of CVE-2023-25756 is improper bounds checking in the BIOS firmware code. When processing certain data structures or memory operations, the firmware fails to adequately validate that read operations remain within the allocated buffer boundaries. This allows memory contents beyond the intended buffer to be accessed, which can expose sensitive information or be leveraged as part of a privilege escalation chain.

Attack Vector

The attack vector for this vulnerability requires:

1. Authentication: The attacker must first gain authenticated access to the target system
2. Adjacent Network Access: The attacker must be on the same network segment as the target (e.g., same LAN, shared network infrastructure)
3. BIOS Firmware Interaction: The attacker must trigger the vulnerable code path in the BIOS firmware

The adjacent network requirement limits exploitation to scenarios where attackers have already established a foothold on the local network. This could occur through compromised network devices, insider threats, or physical proximity in shared network environments.

The vulnerability affects the BIOS firmware directly, meaning exploitation occurs at a low level in the system architecture, potentially before operating system security controls are active.

Detection Methods for CVE-2023-25756

Indicators of Compromise

• Unexpected BIOS configuration changes or settings modifications
• Anomalous firmware-level activity detected by hardware security modules or TPM attestation failures
• Unusual adjacent network traffic patterns targeting system management interfaces
• Evidence of privilege escalation from authenticated but low-privilege accounts

Detection Strategies

• Implement firmware integrity monitoring using Trusted Platform Module (TPM) measurements and Secure Boot validation
• Monitor for unusual SMM (System Management Mode) activity or BIOS-level operations
• Deploy network segmentation monitoring to detect unusual adjacent network access patterns
• Enable detailed logging of authentication events and correlate with system-level privilege changes
• Utilize endpoint detection and response (EDR) solutions capable of detecting firmware-level anomalies

Monitoring Recommendations

• Regularly verify BIOS firmware integrity through cryptographic hash comparisons against known-good firmware images
• Implement network access control (NAC) to limit adjacent network access to authorized devices
• Monitor Intel Management Engine (ME) and BIOS update mechanisms for unauthorized modifications
• Deploy SentinelOne agents to detect suspicious system behavior that may indicate firmware-level compromise

How to Mitigate CVE-2023-25756

Immediate Actions Required

• Identify all systems with affected Intel processors by conducting a comprehensive hardware inventory
• Apply the latest BIOS firmware updates from system manufacturers as they become available
• Implement network segmentation to limit adjacent network access to critical systems
• Review and restrict authentication to systems with vulnerable firmware
• Enable Secure Boot and TPM-based firmware verification where supported

Patch Information

Intel has released security advisory Intel SA-00924 addressing this vulnerability. System administrators should check with their OEM hardware vendors (Dell, HP, Lenovo, etc.) for BIOS firmware updates specific to their systems. The firmware updates address the out-of-bounds read condition by implementing proper bounds checking in the affected code paths.

NetApp has also published advisory NTAP-20231221-0008 for affected NetApp products using Intel processors.

Workarounds

• Restrict network access to management interfaces and limit adjacent network connectivity to trusted devices only
• Implement strong authentication controls and monitor for unauthorized access attempts
• Enable hardware-based security features such as Secure Boot and UEFI firmware protections
• Consider network isolation for systems that cannot be immediately patched

# Example: Check current BIOS version on Linux systems
sudo dmidecode -s bios-version

# Verify Secure Boot status
mokutil --sb-state

# Check TPM status for firmware attestation support
cat /sys/class/tpm/tpm0/device/description 2>/dev/null || echo "TPM not detected"