Windows Kernel EUVD-2026-56651

Exploitation requires an authenticated local session on the target system - the CVSS vector PR:L confirms that a low-privileged account (e.g., standard user) is sufficient. AV:L confirms this is a local-only attack; remote unauthenticated exploitation is not possible based on available data. AC:H indicates that exploitation is not straightforward: specific timing, race conditions, or kernel memory layout conditions must be satisfied, reducing the likelihood of reliable exploitation without significant development effort. Exploitation is limited to Windows 11 versions 24H2, 25H2, and 26H1, and Windows Server 2025 (including Server Core) running unpatched builds. No non-default configuration or specific feature enablement is identified as a prerequisite beyond standard local logon access.

The CVSS base score of 7.0 with vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H accurately reflects the realistic exploitation difficulty: an attacker must already hold local authenticated access (PR:L) and must navigate high-complexity conditions (AC:H), such as race conditions or careful memory-layout manipulation typical of kernel UAF exploitation. Impact is complete (C:H/I:H/A:H) once exploitation succeeds, consistent with the Denial of Service tag alongside privilege escalation. This vulnerability is not listed in the CISA KEV catalog and no public proof-of-concept exploit has been identified, which meaningfully reduces near-term operational risk compared to its CVSS score in isolation. EPSS data is not available in the provided intelligence, limiting probabilistic exploitation forecasting. Real-world priority is moderate-to-high for Windows-heavy enterprise environments - the affected version scope (Windows 11 24H2/25H2/26H1 and Server 2025) covers current-generation deployments, but the AC:H barrier substantially limits opportunistic exploitation.

A low-privileged local user - such as a standard domain account or an attacker who has achieved initial foothold via phishing - crafts a sequence of kernel object allocations and frees designed to reclaim freed memory at a predictable address, then triggers the vulnerable code path to access the freed region and overwrite kernel control structures. This yields SYSTEM-level execution on the targeted Windows 11 or Server 2025 host. No public exploit code has been identified at time of analysis, but the high-complexity requirement indicates that a functional exploit would require targeted kernel heap-manipulation research.