Windows DWM EUVD-2026-100109

Exploitation requires the attacker to already have a local, interactive or authenticated low-privileged session on the target Windows host (PR:L, AV:L) and the ability to execute code that invokes the Desktop Window Manager (DWM) Core Library - a component active on standard Windows desktop sessions and RDP session hosts. No user interaction is required (UI:N) and complexity is low (AC:L), but the vulnerability cannot be reached remotely or from an unauthenticated position, which meaningfully limits exposure to scenarios where an attacker has already gained an initial foothold (e.g., malware, a compromised standard account, or multi-user/shared hosts). Patched builds per the Microsoft advisory (e.g., Windows 11 24H2 >=10.0.26100.9711, Server 2025 >=10.0.26100.33650, Server 2019/Windows 10 1809 >=10.0.17763.9376) are not vulnerable.

This is a credible but not emergency-grade priority. The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, 7.8 HIGH) describes a local, low-complexity privilege escalation requiring an already-authenticated low-privileged attacker - consistent with the description's 'authorized attacker to elevate privileges locally.' CISA's SSVC framework reinforces a measured posture: Exploitation=none (no observed or public exploitation), Automatable=no (requires local foothold and cannot be mass-sprayed), but Technical Impact=total (successful exploitation yields full control, matching the C:H/I:H/A:H and typical DWM-to-SYSTEM escalation). No KEV listing and no POC are indicated in the input, and no EPSS score was provided, so the probabilistic exploitation signal is simply absent rather than low. The signals are internally consistent: high technical impact but gated behind local access and prior authentication, and no evidence of active exploitation. Treat as an important patch-cycle item (especially on multi-user/shared or kiosk hosts and RDP session hosts where low-priv users are present), not a drop-everything zero-day. EPSS data is missing from the input and should be checked before final prioritization.

A low-privileged user (or malware already running under a standard account) executes a crafted program that drives the Windows DWM Core Library into an out-of-bounds read, corrupting adjacent state to hijack execution in a higher-privileged context. The result is escalation to SYSTEM, enabling full control of the host. No public exploit is identified at time of analysis, and local access plus an existing user session are prerequisites.