CVE-2024-21302 is an elevation of privilege vulnerability affecting Microsoft Windows 10 Version 1809 and other Windows versions including Windows 11 and Windows Server 2016 and later that support Virtualization-Based Security (VBS). VBS is a security feature that uses hardware virtualization to create and isolate a secure region of memory from the normal operating system, protecting sensitive data and processes. This vulnerability allows an attacker who already has administrator privileges on the affected system to replace current Windows system files with outdated versions. By doing so, the attacker can reintroduce previously mitigated vulnerabilities, effectively bypassing some of the protections offered by VBS. This can lead to unauthorized data exfiltration of information that VBS is designed to protect. The vulnerability is particularly impactful on systems running Azure Virtual Machines SKUs that support VBS. Microsoft has released an opt-in revocation policy mitigation in August 2024 (KB5042562) that allows organizations to block rollback of VBS-related updates, but this mitigation carries risks and should be carefully evaluated before deployment. The vulnerability has a CVSS 3.1 base score of 6.7, indicating a medium severity level. Exploitation requires administrative privileges but no user interaction, and it affects confidentiality, integrity, and availability by enabling rollback to vulnerable system files and bypassing security features. No known exploits are reported in the wild at this time. Organizations are advised to monitor Microsoft Security Update Guide for official patches and consider the opt-in mitigation after assessing its impact on their environment.

For European organizations, this vulnerability poses a significant risk particularly to enterprises and government entities relying on Windows 10 Version 1809 or later versions with VBS enabled, including those using Azure Virtual Machines. The ability to rollback system files to outdated versions undermines the integrity of security controls and could allow attackers to exploit previously fixed vulnerabilities, potentially leading to data breaches or system compromise. This is especially critical for sectors handling sensitive or regulated data such as finance, healthcare, and critical infrastructure. The circumvention of VBS protections could expose cryptographic keys, credentials, or other sensitive information protected by hardware virtualization. Since exploitation requires administrative privileges, the threat is heightened in environments where privilege escalation or insider threats are possible. The lack of a fully released patch means organizations must rely on the opt-in mitigation or other compensating controls, which may introduce operational risks or complexity. Overall, the vulnerability could lead to significant confidentiality, integrity, and availability impacts if exploited in European organizations.

1. Immediately review and consider implementing the opt-in revocation policy mitigation described in Microsoft KB5042562 to block rollback of VBS-related updates. Evaluate the operational risks associated with this mitigation in a test environment before deployment. 2. Enforce strict administrative privilege management and monitoring to reduce the risk of attackers gaining the required elevated privileges to exploit this vulnerability. 3. Employ robust endpoint detection and response (EDR) solutions capable of detecting unusual system file modifications or rollback attempts. 4. Regularly audit and verify the integrity of critical Windows system files, especially those related to VBS components, using tools like System File Checker (SFC) or Windows Defender System Guard. 5. Maintain up-to-date backups and recovery plans to restore systems to a secure state if rollback or tampering is detected. 6. Subscribe to Microsoft Security Update Guide notifications to promptly apply official patches once released. 7. For organizations using Azure VMs, review VM SKU configurations and consider upgrading to newer Windows versions with improved security features and patches. 8. Implement network segmentation and least privilege principles to limit the spread and impact of potential exploitation.