CVE-2024-37973 is a vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) characterized by uncontrolled recursion that results in a Secure Boot security feature bypass. Secure Boot is a critical security mechanism designed to ensure that only trusted software is loaded during the system startup process, preventing rootkits and bootkits from compromising the system at a low level. The vulnerability arises from improper handling of recursion within the Secure Boot code path, which can be exploited remotely (attack vector: adjacent network) without requiring any privileges or user interaction. This flaw allows an attacker to bypass Secure Boot protections, potentially enabling the execution of unauthorized code during the boot process. The CVSS v3.1 base score of 8.8 reflects the high impact on confidentiality, integrity, and availability, as exploitation could lead to full system compromise. Although no exploits are currently known in the wild, the vulnerability's nature and impact make it a critical concern. The vulnerability is tracked under CWE-674 (Uncontrolled Recursion), indicating that the recursive calls are not properly bounded, leading to unexpected behavior or crashes that can be leveraged for bypassing security controls. No patches were available at the time of disclosure, emphasizing the need for proactive mitigation strategies. The vulnerability affects a widely deployed Windows version, increasing the potential attack surface significantly.

For European organizations, the impact of CVE-2024-37973 is substantial. Exploitation could allow attackers to bypass Secure Boot, undermining the foundational trust model of system integrity and enabling persistent, stealthy malware infections that survive reboots and evade detection. This can lead to severe confidentiality breaches, data theft, and disruption of critical services. Industries relying on Windows 10 Version 1809, including government agencies, healthcare, finance, and critical infrastructure, face heightened risks of operational disruption and reputational damage. The vulnerability's remote attack vector and lack of required privileges make it accessible to a broad range of threat actors, increasing the likelihood of targeted attacks or widespread exploitation once exploit code becomes available. Additionally, the absence of user interaction requirements facilitates automated attacks, potentially impacting large numbers of systems rapidly. The inability to trust the Secure Boot process can also complicate incident response and recovery efforts, as attackers may maintain persistence at a low system level.

Given the absence of an official patch at the time of disclosure, European organizations should prioritize the following mitigation steps: 1) Upgrade affected systems to a newer, supported Windows version where the vulnerability is addressed, or apply Microsoft’s security updates immediately upon release. 2) Implement network segmentation and strict access controls to limit exposure of vulnerable systems, especially restricting adjacent network access to trusted devices only. 3) Enable and enforce additional endpoint security measures such as Endpoint Detection and Response (EDR) solutions capable of detecting anomalous boot-time behaviors. 4) Monitor system logs and network traffic for unusual activity indicative of Secure Boot bypass attempts or recursive call anomalies. 5) Consider deploying hardware-based root of trust mechanisms or enhanced firmware protections where feasible to supplement Secure Boot. 6) Maintain up-to-date backups and incident response plans tailored to boot-level compromise scenarios. 7) Educate IT staff about the vulnerability specifics to ensure rapid identification and response. These targeted actions go beyond generic patching advice and address the unique challenges posed by Secure Boot bypass vulnerabilities.