Hvci Bypass ((link)) -

But Lodestone had broken it.

To understand the impact of a bypass, one must first grasp the foundation of the protection itself. HVCI is a core feature of Microsoft’s Virtualization-Based Security (VBS) introduced in Windows 10, Windows 11, and Windows Server 2016.

While HVCI prevents code patching, "data-only" attacks remain a threat. The "Hell's Hollow" technique utilizes the undocumented Alternate System Call handler to hook the System Service Dispatch Table (SSDT) by manipulating the KTRAP_FRAME rather than overwriting code. However, it is critical to note that while Hell's Hollow resists PatchGuard and HyperGuard, HVCI specifically blocks writing to the PspServiceDescriptorGroupTable structure , leaving this vector mitigated. Researchers are actively exploring "pure data" SSDT Hijack primitives that hijack execution flow without touching code integrity checks.

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

HVCI is a feature of Virtualization-Based Security (VBS) in Windows 10/11 and Windows Server 2016+. It uses the Windows hypervisor to create a secure, isolated environment for code integrity checks, separate from the main operating system kernel. How HVCI Protects the Kernel

The most common method for bypassing HVCI is the "Data-Only" attack. Since HVCI prevents the execution of new code (shellcode), attackers shift their focus to manipulating existing code. Instead of injecting a malicious payload, an attacker with kernel read/write capabilities (obtained via a BYOVD exploit) will target critical data structures. For example, an attacker might target the Token property of a process object to elevate privileges. By swapping the token of a low-privilege process with that of a SYSTEM process, the attacker achieves their goal without ever injecting executable code. Because the attacker is only modifying data pointers—not executing unsigned code—HVCI’s strict code integrity policies are not triggered.

: The hypervisor uses Second Level Address Translation (SLAT) and Extended Page Tables (EPT) to mark kernel memory pages as Read-Execute (R-X) or Read-Write (R-W) . But Lodestone had broken it

To counter BYOVD attacks, Windows maintains a cloud-updated kernel driver blocklist. If a signed driver is found to have vulnerabilities that allow attackers to read/write kernel memory, its certificate signature hash is blacklisted, preventing it from loading on systems with HVCI enabled.

: Utilize advanced threat protection and monitoring tools to detect and mitigate sophisticated attacks.

Some commercial tools (e.g., for red teams) advertise "HVCI bypass" as a feature to test defenses. Example features: Researchers are actively exploring "pure data" SSDT Hijack

to load older, signed-but-flawed drivers. If these drivers aren't on the HVCI revocation list, they can be used to gain a kernel-mode write primitive, though they still face HVCI's restrictions on creating new executable code. how to detect these types of low-level hypervisor attacks?

HVCI operates by creating a secure environment called Virtualization-Based Security (VBS). It utilizes a hypervisor (Hyper-V) to manage memory page permissions:

In standard operating systems, kernel-mode code executes with the highest level of privileges. If an attacker compromises the kernel, they gain absolute control over the system. HVCI mitigates this threat by isolating the page table management and code signing verification processes within a secure Virtual Trust Level 1 (VTL1) container, completely segregated from the normal kernel (VTL0). Even if malware achieves kernel-level execution privileges, it cannot modify executable pages or inject unsigned code into the kernel space, effectively breaking the standard post-exploitation playbook. The Architecture of HVCI: How It Works

Offensive security research has highlighted several specific strategies used to achieve arbitrary kernel code execution under active HVCI protections. Vector A: Bring Your Own Vulnerable Driver (BYOVD)