CVE-2024-26250 is a vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) that pertains to a protection mechanism failure classified under CWE-693. Specifically, this vulnerability involves a bypass of the Secure Boot security feature. Secure Boot is a critical security mechanism designed to ensure that only trusted software is loaded during the system startup process, preventing unauthorized or malicious code from executing before the operating system loads. The bypass of this mechanism means that an attacker with sufficient privileges could circumvent Secure Boot protections, potentially allowing the execution of unsigned or malicious bootloaders or kernel-level code. This could lead to a complete compromise of system integrity, confidentiality, and availability. The CVSS v3.1 base score is 6.7 (medium severity), with the vector indicating that the attack requires local access (AV:L), low attack complexity (AC:L), high privileges (PR:H), no user interaction (UI:N), and impacts confidentiality, integrity, and availability (C:H/I:H/A:H). The scope remains unchanged (S:U), and the exploit code maturity is unofficial (E:U), with remediation level official (RL:O) and report confidence confirmed (RC:C). No known exploits in the wild have been reported to date, and no patches have been linked yet. The vulnerability's nature suggests that it is exploitable only by users with high privileges on the affected system, and it does not require user interaction, making it a significant risk in environments where privileged access is attainable by attackers or malicious insiders. Given that Windows 10 Version 1809 is an older release, many organizations may have already migrated to newer versions, but legacy systems still in operation remain vulnerable. The failure in Secure Boot protection could facilitate persistent malware infections, rootkits, or bootkits that evade detection by traditional security controls.

For European organizations, the impact of this vulnerability could be substantial, especially in sectors relying on legacy Windows 10 Version 1809 systems, such as industrial control systems, healthcare, government, and critical infrastructure. A Secure Boot bypass undermines the trustworthiness of the boot process, enabling attackers to implant persistent, stealthy malware that can evade endpoint detection and response tools. This could lead to data breaches involving sensitive personal or corporate data, disruption of critical services, and potential regulatory non-compliance under GDPR and other data protection laws. The requirement for high privileges limits exploitation to scenarios where attackers have already gained significant access, but once exploited, the attacker could maintain long-term control over affected systems. This could facilitate lateral movement within networks, espionage, sabotage, or ransomware deployment. The absence of known exploits in the wild currently reduces immediate risk, but the vulnerability's presence in widely used operating systems means that threat actors may develop exploits, increasing future risk. Organizations with legacy systems that cannot be easily upgraded are particularly at risk, as they may lack the latest security improvements and mitigations.

1. Upgrade affected systems: The most effective mitigation is to upgrade Windows 10 Version 1809 systems to a supported and patched version of Windows 10 or Windows 11 that addresses this vulnerability. 2. Restrict privileged access: Limit administrative privileges strictly to necessary personnel and implement robust privilege access management (PAM) controls to reduce the risk of local privilege abuse. 3. Enable and enforce Secure Boot policies: Verify Secure Boot is enabled and properly configured in UEFI firmware settings to prevent unauthorized bootloaders. 4. Implement endpoint detection and response (EDR) solutions capable of detecting boot-level anomalies and rootkit behaviors. 5. Monitor system integrity: Use tools that verify bootloader and kernel integrity, such as Windows Defender System Guard or third-party integrity monitoring solutions. 6. Network segmentation: Isolate legacy systems to limit lateral movement if compromised. 7. Incident response readiness: Prepare for potential exploitation by establishing monitoring for privilege escalation attempts and unusual boot process modifications. 8. Firmware updates: Ensure UEFI firmware is up to date to support Secure Boot enforcement and mitigate related vulnerabilities. 9. Disable unnecessary local accounts and services that could be leveraged to gain high privileges. 10. Regularly audit and review security configurations and logs for signs of tampering or exploitation attempts.