Windows DWM EUVD-2026-56687

The attacker must hold a valid local user account with at minimum standard (low-privilege) rights on the target system, consistent with CVSS PR:L. The attack vector is strictly local (AV:L): the attacker must be able to execute code on the machine, either via interactive console logon, an active Remote Desktop session, or a pre-existing foothold obtained through a separate vulnerability. No special Windows feature, non-default configuration setting, or elevated privilege is required beyond standard user access. No second-user interaction is required (UI:N). Exploitation is bounded by the requirement for local code execution - a purely remote, unauthenticated attacker cannot directly trigger this vulnerability without first establishing local access through another means.

The CVSS 7.8 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects a realistic and low-friction exploitation scenario: any standard domain or local user account is sufficient, no additional complexity or user interaction is required, and the outcome is full compromise of the vulnerable system. The High ratings across all three impact dimensions confirm the potential for complete SYSTEM-level takeover. No EPSS data was included in the provided intelligence, so probabilistic exploitation likelihood cannot be quantified from this analysis. KEV status is not confirmed, meaning active exploitation has not been corroborated by CISA at time of analysis - however, the absence of a KEV listing does not indicate safety, particularly given that use-after-free primitives in Windows kernel-adjacent subsystems like DWM historically attract rapid weaponization post-disclosure. The breadth of affected versions - spanning consumer Windows 10, current Windows 11 branches, and both server generations - means the aggregate exposure is substantial even if per-system exploitation probability is moderate. No conflicting signals exist between the CVSS vector and the described local attack surface; the vector is internally consistent with the vulnerability class.

A low-privileged user logged into an unpatched Windows workstation - or connected via Remote Desktop - crafts a sequence of window management or graphical API calls to cause DWM to free a heap object while retaining a live pointer to it. The attacker then performs a heap spray to occupy the freed region with controlled data, causing DWM to dereference attacker-controlled content and redirect execution to shellcode or a ROP chain running in the privileged DWM service context, yielding SYSTEM-level code execution. No public proof-of-concept code has been identified at time of analysis.