CVE-2022-4575 in ThinkPad BIOS
Summary
by MITRE • 10/30/2023
A vulnerability due to improper write protection of UEFI variables was reported in the BIOS of some ThinkPad models could allow an attacker with physical or local access and elevated privileges the ability to bypass Secure Boot.
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Analysis
by VulDB Data Team • 11/22/2023
This vulnerability resides in the firmware level of certain ThinkPad devices where UEFI variables lack proper write protection mechanisms. The flaw represents a critical security weakness that undermines the fundamental security model of modern computing platforms. UEFI variables serve as critical configuration points that control system behavior including boot processes, security settings, and hardware initialization parameters. When these variables are not properly protected against unauthorized modification, they create a pathway for malicious actors to manipulate core system functionality.
The technical implementation of this vulnerability stems from inadequate access controls within the UEFI firmware implementation. Specifically, the BIOS firmware fails to enforce proper write permissions on critical UEFI variables that should remain protected from modification by unauthorized entities. This misconfiguration allows attackers with physical access to the device and local elevated privileges to modify these variables directly through firmware interfaces. The vulnerability is particularly concerning because UEFI variables often control Secure Boot policies and other critical boot-time security mechanisms that are designed to prevent unauthorized code execution.
From an operational perspective, this vulnerability creates a significant attack surface that can be exploited by adversaries with relatively low privileges and physical access to target systems. The impact extends beyond simple privilege escalation as it fundamentally compromises the integrity of the boot process and the security chain that Secure Boot is designed to establish. An attacker could modify UEFI variables to disable Secure Boot, install malicious boot loaders, or modify system configuration parameters that could persist across reboots. This represents a complete bypass of the security model that modern operating systems rely upon for protection against rootkits and boot-level malware.
The exploitation of this vulnerability aligns with techniques described in the ATT&CK framework under the T1068 - Exploitation for Privilege Escalation and T1542 - Pre-OS Boot categories. The weakness can be categorized as a CWE-284 - Improper Access Control, specifically manifesting as inadequate protection of UEFI variables within the system firmware. Organizations should implement immediate mitigations including firmware updates from Lenovo, which address the write protection mechanisms, and enhanced physical security measures. Additionally, system administrators should consider implementing hardware-based security features such as Trusted Platform Module (TPM) binding and firmware integrity monitoring solutions to detect unauthorized modifications. The vulnerability demonstrates the critical importance of firmware security and the need for comprehensive security approaches that address both software and hardware components of modern computing systems.