CVE-2025-59033 is a vulnerability categorized under CWE-420 (Unprotected Alternate Channel) and CWE-693 (Protection Mechanism Failure) affecting Microsoft Windows 10. The core issue lies in the implementation of the Microsoft vulnerable driver blocklist, which is enforced via Windows Defender Application Control (WDAC) policies. WDAC is designed to prevent unauthorized or malicious drivers from loading by blocking based on code signer certificates. When entries specify only the to-be-signed (TBS) portion of the code signer certificate, the blocklist functions correctly. However, if entries include the signing certificate's TBS hash combined with a 'FileAttribRef' qualifier—such as file name or version—these entries may not be blocked as intended. This bypass occurs regardless of whether Hypervisor-Protected Code Integrity (HVCI) is enabled, undermining a key security control. The vulnerability allows attackers to load malicious or unsigned drivers, potentially leading to full system compromise, including elevated privileges, data theft, or denial of service. Microsoft disputes the CVE assignment, arguing the blocklist is intended for use with HVCI, but the vulnerability remains significant given the potential for bypass. The CVSS v3.1 score is 7.4 (high), reflecting local attack vector, high complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. No patches or known exploits are currently reported, but the vulnerability's nature suggests it could be leveraged in targeted attacks against Windows 10 endpoints.

For European organizations, the impact of CVE-2025-59033 could be severe. Many enterprises and government agencies across Europe rely on Windows 10 with WDAC and HVCI for endpoint security. Successful exploitation could allow attackers to load malicious drivers, bypassing security controls and gaining kernel-level access. This can lead to data breaches, espionage, ransomware deployment, or disruption of critical services. Confidentiality is at risk due to potential data exfiltration; integrity is compromised as attackers can alter system behavior; availability can be affected by destabilizing or disabling systems. The vulnerability's bypass of HVCI protections is particularly concerning for organizations that depend on hardware-enforced security. Given the high complexity of exploitation but no need for privileges or user interaction, sophisticated threat actors could weaponize this vulnerability in targeted campaigns. The lack of known exploits currently provides a window for proactive mitigation, but the risk remains high due to the critical nature of the affected systems.

European organizations should implement the following specific mitigations: 1) Review and audit WDAC policies to identify any entries using the signing certificate's TBS hash combined with 'FileAttribRef' qualifiers, and remove or modify these entries to rely solely on the TBS part of the certificate. 2) Enforce strict code signing policies that avoid qualifiers that may cause bypasses. 3) Enable and maintain HVCI and ensure it is properly configured and updated, as it provides an additional layer of protection despite the vulnerability. 4) Monitor system logs and WDAC enforcement events for anomalies indicating potential driver loading bypass attempts. 5) Employ endpoint detection and response (EDR) solutions capable of detecting suspicious driver loads or kernel-level anomalies. 6) Stay updated with Microsoft advisories and apply patches promptly once available. 7) Conduct penetration testing and red team exercises simulating driver blocklist bypass to validate defenses. 8) Limit administrative privileges and restrict driver installation rights to reduce attack surface. These steps go beyond generic advice by focusing on WDAC policy hygiene and proactive detection tailored to this vulnerability's specifics.