Understanding the Architecture, Exploitation, and Defense of Hypervisor-Protected Code Integrity (HVCI) Bypasses
Because an attacker in VTL 0 cannot simply write and execute memory, they must rely on architectural loopholes, code reuse, or hardware flaws to achieve an HVCI bypass.
To understand how HVCI is bypassed, one must first understand how it establishes its security boundaries. HVCI relies on Virtualization-Based Security (VBS) to divide the operating system into distinct virtual trust levels (VTLs). Hvci Bypass
An HVCI bypass effectively resets the security posture to a pre-VBS era, allowing attackers to:
As bypass vectors shift from code injection to structural and data-only attacks, Microsoft and hardware manufacturers have introduced cascading layers of defense to protect HVCI. Driver Blocklists and WDAC An HVCI bypass effectively resets the security posture
Since an attacker cannot inject unsigned shellcode directly into memory, they rely on code that is already legitimately signed and trusted by Windows. What is HVCI? | CORSAIR
to ensure only signed kernel-mode code can execute. Because it operates at the hypervisor level using Extended Page Tables (EPT), it prevents memory from being both writable and executable (RWX), making it difficult to patch the kernel or load malicious drivers. Common HVCI Bypass Methods | CORSAIR to ensure only signed kernel-mode code
As bypass techniques evolve, Windows has introduced multi-layered mitigations designed to close the gaps exploited by attackers.
The most direct bypass is to simply flip the global flag that tells the hypervisor to enforce HVCI. Inside the kernel ( ntoskrnl.exe ), there are global variables such as g_CiOptions or g_HvlpVsmEnabled .
: This is increasingly difficult on newer hardware with Intel CET (Control-Flow Enforcement Technology) , which protects return addresses via a shadow stack. 2. Exploiting "Bring Your Own Vulnerable Driver" (BYOVD)
To audit your system's VBS and HVCI status, execute msinfo32.exe and review the "Virtualization-based security" entries.