Windows VBS Enclave EUVD-2026-99649

Exploitation requires the attacker to already have local, authorized (low-privilege, PR:L) code execution on the target and to reach the Windows Virtualization-Based Security (VBS) Enclave code path, where a crafted value triggers an integer overflow (CWE-190). Limiting factors: this is a local-only vector (AV:L) with no remote or network-facing exposure, so it cannot be used for initial access and functions only as a post-compromise escalation; the host must be running an affected, unpatched Windows 11 build (26H2 <10.0.26300.9711, 25H2/24H2 <...9711, 26H1 <10.0.28000.3231, 23H2 <10.0.22631.7652); and VBS must be active for the enclave attack surface to be present, which is default on many modern Windows 11 devices but can be disabled. No user interaction is required (UI:N).

The input CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, base 7.8) describes a classic local privilege-escalation primitive: the attacker must already have a foothold (AV:L) and some level of authorization (PR:L), but needs no user interaction and faces low attack complexity, yielding full CIA impact on the host. This is consistent with the description's 'authorized attacker to elevate privileges locally.' No EPSS score was provided in the input, so exploitation probability cannot be quantified. The vulnerability is NOT listed in CISA KEV and no public POC is referenced, so there is no public exploit identified at time of analysis. Signals are internally consistent (no network-vs-local contradiction), so this reads as a genuine but not emergency priority: a standard Patch-Tuesday-class local EoP that becomes dangerous as a second-stage escalation after initial access, rather than a remotely wormable threat. Because it affects the VBS Enclave trust boundary, successful exploitation can undermine a security feature specifically designed to isolate secrets, which raises its value to post-compromise attackers above a generic EoP. Missing signals to verify with the vendor: EPSS probability and any in-the-wild telemetry.

An attacker who has already gained low-privileged code execution on a Windows 11 host (e.g., via phishing or a compromised standard user account) invokes the vulnerable VBS Enclave code path with crafted input that triggers an integer overflow, corrupting memory to gain SYSTEM-level privileges. No user interaction is required and attack complexity is low. No public exploit is identified at time of analysis, so weaponization would require the attacker to develop the exploit.