CVE-2016-5247 in ThinkCentre
Summary
by MITRE
The BIOS for Lenovo ThinkCentre E93, M6500t/s, M6600, M6600q, M6600t/s, M73p, M800, M83, M8500t/s, M8600t/s, M900, M93, and M93P devices; ThinkServer RQ940, RS140, TS140, TS240, TS440, and TS540 devices; and ThinkStation E32, P300, and P310 devices might allow local users or physically proximate attackers to bypass the Secure Boot protection mechanism by leveraging an AMI test key.
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Analysis
by VulDB Data Team • 09/19/2022
This vulnerability affects a critical security mechanism in Lenovo ThinkCentre, ThinkServer, and ThinkStation devices that utilize AMI BIOS firmware. The flaw resides in the Secure Boot implementation where the system fails to properly validate the authenticity of boot components, creating a pathway for attackers to circumvent the intended security protections. The vulnerability specifically exploits the presence of an AMI test key within the BIOS firmware that should never be present in production environments, allowing unauthorized code execution during the boot process. The impact is significant because Secure Boot is designed to prevent malicious code from executing during system initialization, which is a fundamental defense against rootkits and bootkits that target the earliest stages of system operation.
The technical exploitation of this vulnerability requires either local access or physical proximity to the target system, making it particularly concerning for enterprise environments where devices may be left unattended or where physical security controls are inadequate. Attackers can leverage the AMI test key to sign malicious boot loaders or kernel modules, effectively bypassing the cryptographic verification processes that Secure Boot is designed to enforce. This creates a persistent backdoor that can survive system reboots and remains operational until the firmware is updated or the test key is removed. The vulnerability demonstrates a failure in firmware security practices where testing artifacts were not properly removed from production builds, violating established security principles and creating a persistent threat vector.
The operational impact extends beyond simple privilege escalation as this vulnerability undermines the entire system integrity framework. Organizations using affected Lenovo devices face potential compromise of their entire infrastructure since the attack occurs at the firmware level, making traditional endpoint protection solutions ineffective. The vulnerability affects multiple device families across different product lines, indicating a systemic issue within Lenovo's firmware development and quality assurance processes. This widespread impact means that enterprise security teams must conduct comprehensive inventory assessments to identify all affected devices, potentially involving hundreds or thousands of systems across various departments and locations.
Organizations should implement immediate mitigations including firmware updates from Lenovo, which address the presence of the test key in the BIOS implementations. Network segmentation and physical security controls should be enhanced to prevent unauthorized access to affected systems, particularly in environments where devices are located in unsecured areas. Security monitoring should focus on detecting unusual boot patterns or unexpected code signatures that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1014 (Rootkit) and CWE-310 (Cryptographic Vulnerability) categories, highlighting the intersection of firmware-level attacks with established threat frameworks. Regular firmware audits and supply chain security reviews become essential practices to prevent similar issues in the future, as this vulnerability represents a failure in the secure development lifecycle where testing artifacts were not properly sanitized before production deployment.