CVE-2024-37986 is a high-severity integer underflow vulnerability (CWE-191) affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability specifically targets the Secure Boot security feature, which is designed to ensure that only trusted software is loaded during the system startup process. An integer underflow occurs when an arithmetic operation causes a value to wrap around below its minimum representable value, potentially leading to unexpected behavior or security bypasses. In this case, the underflow can be exploited to bypass Secure Boot protections, allowing an attacker to load unauthorized or malicious code during the boot process. The CVSS 3.1 base score of 8.0 reflects the vulnerability's high impact on confidentiality, integrity, and availability, with an attack vector requiring adjacent network access (AV:A), low attack complexity (AC:L), no privileges required (PR:N), but user interaction is needed (UI:R). The scope is unchanged (S:U), and the impact is high across confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits are currently reported in the wild, and no patches have been linked yet. This vulnerability poses a significant risk because Secure Boot is a critical security control that prevents rootkits and bootkits from compromising the system at a fundamental level. Exploiting this flaw could allow attackers to persist undetected, escalate privileges, and compromise system integrity from the earliest stage of system operation.

For European organizations, this vulnerability presents a serious threat, especially for enterprises and government agencies relying on Windows 10 Version 1809 in their infrastructure. Bypassing Secure Boot undermines the trusted computing base, enabling attackers to deploy persistent malware that can evade traditional detection mechanisms. This can lead to data breaches, espionage, ransomware attacks, and disruption of critical services. Organizations in regulated sectors such as finance, healthcare, and critical infrastructure may face compliance violations and operational risks. The requirement for user interaction and adjacent network access somewhat limits remote exploitation but does not eliminate risk in environments where attackers can trick users or have local network presence. Legacy systems still running Windows 10 Version 1809, which is an older release, may be particularly vulnerable if not updated or patched promptly. The lack of available patches increases the urgency for mitigation. Overall, the vulnerability could facilitate advanced persistent threats (APTs) targeting European entities, potentially impacting confidentiality, integrity, and availability of sensitive data and systems.

1. Immediate mitigation should focus on upgrading affected systems to a newer, supported version of Windows 10 or Windows 11 where this vulnerability is patched or not present. 2. Where upgrades are not immediately feasible, organizations should enforce strict network segmentation to limit adjacent network access, reducing the attack surface. 3. Implement user awareness training to minimize the risk of social engineering attacks that require user interaction. 4. Enable and enforce multi-factor authentication and endpoint detection and response (EDR) solutions that can detect anomalous boot-time or firmware-level behaviors. 5. Monitor system logs and firmware integrity checks for signs of Secure Boot bypass attempts. 6. Disable legacy boot modes (such as CSM or legacy BIOS boot) to enforce Secure Boot usage. 7. Maintain up-to-date backups and incident response plans to quickly recover from potential compromises. 8. Regularly audit and inventory systems to identify those still running Windows 10 Version 1809 and prioritize remediation efforts accordingly.