Windows Kernel EUVD-2026-56334

Exploitation requires a valid, authenticated local session on the target Windows system - at minimum a standard (non-administrative) user account, consistent with CVSS PR:L. The attacker must be able to execute arbitrary code on the system, whether via interactive logon, Remote Desktop Protocol session, or a compromised application context running under a low-privileged account. No non-default configuration or special feature enablement is required; the vulnerability is present in the Windows Kernel across default installations of all affected versions. Exploitation is strictly local (AV:L) - remote unauthenticated exploitation is not possible. Attack complexity is low (AC:L), meaning no race conditions, heap-spray timing dependencies, or environment-specific preconditions are documented. The primary limiting factor is the requirement for prior authenticated access to the target system; systems where remote logon (RDP, WinRM) is restricted to privileged accounts only, or where lateral movement has been blocked, present a harder target.

The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, score 7.8) reflects low attack complexity with a standard user account as the only prerequisite - meaning any authenticated domain or local user could attempt exploitation without needing administrative rights or triggering user interaction. The Scope:Unchanged metric confirms impact is bounded to the compromised host, yet SYSTEM-level privilege escalation is effectively full host compromise. No EPSS score was included in the provided data, limiting probabilistic exploitation forecasting; CISA KEV status is not confirmed. The absence of public exploit code moderates immediate urgency, but the low complexity and broad version coverage (Windows releases spanning approximately 2016-2026) translate to an extremely large attack surface. The combination of minimal privilege requirement, no user interaction, and high impact across all three CIA dimensions makes this a genuine remediation priority, and even organizations operating relatively contained environments with restricted local logon rights should treat patch deployment as time-sensitive.

An attacker who has obtained a standard-privilege Windows account - through credential phishing, password spraying, or lateral movement - logs on locally or via Remote Desktop and invokes a crafted sequence of system calls that triggers the heap-based buffer overflow in the Windows Kernel. The overflow corrupts a kernel security token or adjacent heap metadata, which the attacker manipulates to replace their process token with a SYSTEM token, achieving full administrative control of the host. No public proof-of-concept exploit has been identified at time of analysis.