CVE-2024-21305 is a medium-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). It relates to an incorrect permission assignment (CWE-732) for a critical resource associated with the Hypervisor-Protected Code Integrity (HVCI) security feature. HVCI is designed to enhance kernel-mode code integrity by leveraging virtualization-based security to prevent unauthorized code execution at the kernel level. The vulnerability allows a security feature bypass, meaning that an attacker with high privileges could exploit the improper permission settings to undermine HVCI protections. Specifically, the CVSS vector indicates that the attack requires local access (AV:L), low attack complexity (AC:L), and high privileges (PR:H), but no user interaction (UI:N). The impact is limited to integrity (I:H) with no confidentiality or availability impact. The vulnerability is not known to be exploited in the wild, and no patches have been publicly linked yet. The issue stems from incorrect permission assignments that could allow an attacker with administrative rights to disable or circumvent HVCI, potentially enabling the execution of unauthorized or malicious kernel-mode code. This bypass could facilitate persistence or privilege escalation attacks, undermining the system's security posture.

For European organizations, especially those relying on Windows 10 Version 1809 in critical infrastructure, government, finance, or healthcare sectors, this vulnerability poses a risk to system integrity. While exploitation requires high privileges and local access, an attacker who already has administrative control could leverage this flaw to disable HVCI protections, making subsequent kernel-level attacks easier and harder to detect. This could lead to advanced persistent threats, malware implantation, or rootkit deployment that compromise system integrity and trustworthiness. Organizations with legacy systems still running this older Windows 10 version are particularly vulnerable. The lack of confidentiality and availability impact reduces the risk of data leakage or service disruption directly from this vulnerability, but the integrity compromise could facilitate broader attacks impacting sensitive data or operational continuity indirectly.

Given the absence of a public patch, European organizations should prioritize upgrading or migrating systems from Windows 10 Version 1809 to supported, updated Windows versions with active security support. For systems that must remain on this version, strict access controls should be enforced to limit administrative privileges and local access to trusted personnel only. Employing endpoint detection and response (EDR) solutions that monitor for attempts to disable or bypass HVCI can provide early warning. Additionally, organizations should audit and harden permissions on critical system resources related to HVCI to prevent unauthorized modifications. Regularly reviewing and applying security baselines and group policies that enforce virtualization-based security features can reduce exposure. Network segmentation and limiting lateral movement capabilities can also mitigate the impact if an attacker gains local admin access. Finally, monitoring for unusual kernel-mode code execution or integrity violations can help detect exploitation attempts.