Windows VBS Enclave EUVD-2026-73920

The attacker must have local code execution with at least low-privilege level (PR:L) on an affected, unpatched Windows 11 or Windows Server 2025 system. VBS must be active on the target device - VBS is enabled by default on Windows 11 hardware meeting Secured-Core PC or baseline virtualization requirements, but can be disabled via Group Policy, BIOS settings, or on older hardware that does not support it. The vulnerable code path lies within the VBS Enclave subsystem; interacting with it requires the ability to call enclave-related APIs (e.g., CreateEnclave/LoadEnclaveData), which typically requires a user-mode process context. Exploitation is not remotely triggerable and is not automatable (SSVC: automatable: no). Systems with VBS disabled at the firmware or policy level are not exposed to this specific attack path.

CVSS 3.1 score of 5.5 (Medium) accurately reflects the local attack vector (AV:L), low-privilege requirement (PR:L), and confidentiality-only impact (C:H/I:N/A:N). SSVC corroborates: exploitation is currently none, the attack is not automatable, and technical impact is rated partial. No EPSS score was provided in the input; no CISA KEV listing or public POC code has been identified. Despite the moderate base score, the qualitative risk for environments leveraging VBS Enclaves for secret storage (e.g., credential vaults, cryptographic key material) is elevated - the specific purpose of VBS Enclaves is to protect high-value data, so any read primitive crossing enclave boundaries is more sensitive than a comparable OOB read in general heap memory. Real-world threat is primarily insider threat or post-compromise lateral movement, not opportunistic remote attack. Organizations that have not enabled VBS on Windows 11 hardware are unaffected by this specific path.

A low-privileged local user on an unpatched Windows 11 system invokes VBS Enclave APIs to trigger the out-of-bounds read condition, causing the enclave subsystem to return memory contents from outside the intended read boundary - potentially exposing cryptographic keys, credentials, or other secrets held in adjacent enclave memory. No public exploit code has been identified and the attack is not automatable per SSVC assessment, making this most realistic in insider-threat or post-compromise scenarios where the attacker already holds a local session.