Overview
The world of Cybersecurity is once again on high alert due to a new vulnerability, CVE-2025-59033, discovered within Microsoft’s driver block list. This vulnerability exposes systems without hypervisor-protected code integrity (HVCI) to potential breaches, mainly affecting Windows 10, Windows 11 and Windows Server 2016 and subsequent versions. The severity of this vulnerability becomes apparent when we consider its potential for system compromise or data leakage, making it a high-priority issue for any organization using affected systems.
The vulnerability lies within the Windows Defender Application Control (WDAC) policy implementation. It’s crucial to understand the implication of this vulnerability, considering WDAC is widely used for controlling which applications and files are allowed or blocked in an organization’s Windows environment. This vulnerability, therefore, poses a significant risk to business security and data integrity.
Vulnerability Summary
CVE ID: CVE-2025-59033
Severity: Critical (9.8 CVSS Score)
Attack Vector: Local Network
Privileges Required: Admin Rights
User Interaction: Required
Impact: Potential for system compromise or data leakage
Affected Products
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Product | Affected Versions
Windows 10 | All versions without HVCI
Windows 11 | All versions without HVCI
Windows Server | 2016 and later versions without HVCI
How the Exploit Works
The exploit takes advantage of a flaw in the WDAC policy implementation. On systems that do not have HVCI enabled, entries that specify only the to-be-signed (TBS) part of the code signer certificate are blocked correctly. However, entries that incorporate the signing certificate’s TBS hash along with a ‘FileAttribRef’ qualifier (such as file name or version) will not be blocked. This loophole allows potential attackers to bypass the driver blocklist, potentially leading to a system compromise or data leakage.
Conceptual Example Code
The following pseudocode demonstrates a conceptual exploit for this vulnerability:
def exploit(target_system):
malicious_driver = {
'tbs_hash': '...',
'FileAttribRef': {
'file_name': '...',
'version': '...'
}
}
if not target_system.has_hvci_enabled():
upload_driver(target_system, malicious_driver)
target_system.install_driver(malicious_driver)
compromise_system(target_system)This pseudocode illustrates an attacker creating a malicious driver with a TBS hash and a ‘FileAttribRef’ qualifier, then checking if the target system has HVCI enabled. If HVCI is not enabled, the attacker then uploads and installs the malicious driver, compromising the system. This example highlights the potential severity of this vulnerability and the importance of enabling HVCI or applying the vendor’s patch.
