CVE-2024-28921 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 Secure Boot undermines the system's root of trust, potentially allowing attackers with elevated privileges to execute arbitrary code at boot time, compromise system integrity, and persist undetected. 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), unchanged scope (S:U), and impacts confidentiality, integrity, and availability to a high degree (C:H/I:H/A:H). The exploitability is considered moderate since it requires high privileges and local access, but no user interaction. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in March 2024 and published in April 2024. This issue could be leveraged by attackers who have already gained elevated access to bypass Secure Boot protections, potentially enabling persistent and stealthy attacks such as rootkits or bootkits that compromise system security at a fundamental level.

For European organizations, the impact of this vulnerability can be significant, especially for entities relying on Windows 10 Version 1809 in critical infrastructure, government, finance, healthcare, and industrial control systems. The Secure Boot bypass could allow attackers with local high privileges to install persistent malware that survives reboots and evades traditional detection methods. This undermines system integrity and confidentiality, potentially leading to data breaches, espionage, or sabotage. Organizations with legacy systems or delayed patching cycles are particularly at risk. The requirement for local high privileges limits remote exploitation but does not eliminate risk from insider threats or attackers who have already compromised user accounts with elevated rights. The absence of user interaction reduces the complexity for attackers once they have access. Given the high impact on confidentiality, integrity, and availability, exploitation could disrupt business operations, cause data loss, and damage trust in IT infrastructure security.

1. Upgrade or patch systems: Although no patch links are currently provided, organizations should monitor Microsoft security advisories closely and apply patches as soon as they become available. 2. Upgrade to a supported Windows version: Windows 10 Version 1809 is an older release; migrating to a newer, supported Windows version with updated security features can mitigate this vulnerability. 3. Restrict local administrative privileges: Enforce strict access controls to minimize the number of users with high privileges, reducing the risk of exploitation. 4. Implement endpoint detection and response (EDR): Deploy advanced EDR solutions capable of detecting suspicious boot-level modifications or unauthorized firmware changes. 5. Use hardware-based security features: Leverage Trusted Platform Module (TPM) and hardware-enforced Secure Boot where possible to add layers of protection. 6. Conduct regular audits: Perform security audits and integrity checks on boot configurations and firmware to detect anomalies early. 7. Network segmentation: Limit access to critical systems to reduce the risk of lateral movement by attackers who gain local access. 8. Incident response readiness: Prepare for potential exploitation scenarios by having incident response plans that include boot-level compromise detection and recovery.