Windows DWM EUVD-2026-56338

Exploitation requires an existing local session with at least low-privilege (standard user) access to the target system - remote unauthenticated exploitation is not possible per AV:L/PR:L in the CVSS vector. No user interaction is required beyond the attacker's own actions. The vulnerability is present on default installations of the affected Windows 11 and Server 2025 builds; no special non-default configuration is required to be vulnerable. Exploitation is limited by: the local-only attack vector (attacker must already have code execution or interactive access), the absence of integrity or availability impact (read-only disclosure), the non-automatable nature confirmed by SSVC (cannot be mass-exploited remotely), and restriction to specific Windows builds prior to the fixed versions listed above.

The CVSS 3.1 score of 5.5 with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N reflects a locally exploitable flaw requiring only low privileges and no user interaction, with high confidentiality impact but no integrity or availability consequences. SSVC corroborates a deprioritized posture: exploitation status is none, the attack is not automatable (local vector precludes remote mass exploitation), and technical impact is partial. No EPSS data was provided in source intelligence, which limits probabilistic exploitation forecasting. There is no KEV listing and no identified public proof-of-concept, further supporting a lower operational urgency. The primary real-world risk is use as a data leakage step within a broader attack chain on an already-compromised endpoint - not as an initial access vector. Overall, this is a genuine but non-critical patch that should be addressed in the next routine update cycle rather than emergency response.

A standard domain user with an existing foothold on an unpatched Windows 11 or Server 2025 endpoint executes a crafted local application that triggers the out-of-bounds read in dwmcore during compositing operations, causing DWM to return adjacent heap or stack memory contents. The disclosed memory data could expose credentials, cryptographic material, or other sensitive runtime artifacts that the attacker then leverages to escalate privileges or move laterally. No public exploit code has been identified at time of analysis.