Hvci Bypass

HVCI also remaps kernel memory. Code sections become read-only at the hypervisor level, and data sections become non-executable. Even if an attacker corrupts a page table entry (PTE), the hypervisor’s shadow page tables will override the request, causing a #GP (General Protection Fault) or a VBS violation.

In short, under HVCI, "self-modifying kernel code" becomes impossible.

Microsoft and hardware vendors are not idle. Each bypass leads to new hardening. Hvci Bypass

HVCI runs in Virtual Trust Level 0 (VTL0) , the same as the normal kernel. The hypervisor runs in VTL1. If an attacker can find a bug in the hypervisor-call interface (hypercalls), they might directly manipulate the hypervisor’s memory.

Example: CVE-2019-0887 – An information disclosure in the hypercall HvlSwitchToVsmVtl1 allowed attackers to leak hypervisor memory. While not a full bypass, it paved the way for mapping hypervisor structures. A true vulnerability in the hypervisor’s page table management could allow an attacker to directly modify the SLAT mappings, disabling HVCI for a specific page. HVCI also remaps kernel memory

Like any security mechanism, HVCI is not foolproof. Researchers have identified various vulnerabilities and potential bypass techniques. These can range from software-based exploits that manipulate the system's behavior to hardware vulnerabilities that undermine the virtualization-based protections.

Reports and research on HVCI bypass techniques often detail vulnerabilities or weaknesses in the implementation of HVCI or in other parts of the system that can be exploited to circumvent its protections. These might include: Microsoft and hardware vendors are not idle

HVCI operates by creating a virtualization-based security environment. Here’s a simplified overview of its operation: