CVE-2021-3972 in Notebook
Summary
by MITRE • 04/23/2022
A potential vulnerability by a driver used during manufacturing process on some consumer Lenovo Notebook devices' BIOS that was mistakenly not deactivated may allow an attacker with elevated privileges to modify secure boot setting by modifying an NVRAM variable.
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Analysis
by VulDB Data Team • 05/08/2026
The vulnerability identified as CVE-2021-3972 represents a critical security flaw within the BIOS firmware of certain Lenovo notebook devices that originated during the manufacturing process. This issue stems from a driver component that was inadvertently left active in production systems, creating an exploitable condition that undermines fundamental security mechanisms. The flaw specifically affects consumer-grade Lenovo notebooks where manufacturing drivers intended for internal use were not properly disabled before device deployment to end users.
The technical implementation of this vulnerability involves the manipulation of Non-Volatile Random Access Memory (NVRAM) variables through a persistent driver component. When an attacker with elevated privileges accesses the system, they can leverage this manufacturing driver to modify secure boot settings that are typically protected from unauthorized modification. Secure boot is a critical security feature that prevents unauthorized code from executing during system boot, thereby maintaining the integrity of the boot process and protecting against rootkits and bootkits. The vulnerability essentially creates a backdoor path that allows modification of these protected settings through NVRAM variable manipulation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the system's ability to maintain secure boot integrity. Attackers who can establish elevated privileges on affected systems gain the capability to disable or modify secure boot configurations, potentially enabling the execution of malicious code that would otherwise be blocked by the secure boot mechanism. This represents a significant risk to system integrity and could allow attackers to establish persistent footholds within affected environments. The vulnerability is particularly concerning because it operates at the firmware level, making detection and remediation more complex than typical software vulnerabilities.
From a cybersecurity perspective, this vulnerability aligns with CWE-310, which addresses cryptographic weaknesses, and specifically relates to the improper disabling of security features during manufacturing processes. The ATT&CK framework categorizes this vulnerability under T1068, which involves exploiting legitimate credentials, and potentially T1134, which covers access token manipulation. The flaw demonstrates a critical gap in Lenovo's manufacturing and quality assurance processes, where security configurations intended for internal use were not properly stripped or disabled before product release. Organizations should consider implementing firmware integrity monitoring solutions and conducting regular security assessments of embedded systems to detect similar manufacturing-related security flaws.
Mitigation strategies for CVE-2021-3972 should include immediate firmware updates from Lenovo, which typically address the specific manufacturing driver issue by disabling the problematic component. System administrators should also implement monitoring for unauthorized changes to secure boot settings and conduct thorough inventory assessments to identify affected devices. Additionally, organizations should establish strict protocols for firmware security reviews during manufacturing and deployment phases, ensuring that all temporary or manufacturing-specific drivers are properly disabled before product release. The vulnerability underscores the importance of maintaining security configurations throughout the entire product lifecycle and implementing robust supply chain security practices to prevent similar issues in future deployments.