EUVD-2026-43825
GHSA-v25p-9crm-vx96
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local EoP requiring an authenticated low-priv foothold (AV:L/PR:L), high complexity due to race/state prerequisites (AC:H), yielding full SYSTEM compromise (C/I/A:H).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Improper access control in Windows Win32K allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Win32K kernel-mode subsystem allows an already-authenticated low-privileged user to elevate to SYSTEM through an improper access-control flaw. The issue affects a broad range of Windows client and server releases, from Windows 10 1607 and Windows Server 2012 through Windows 11 26H1 and Windows Server 2025. Microsoft has released a patch; there is no public exploit identified at time of analysis, and the flaw is not listed in CISA KEV.
Technical ContextAI
Win32K (win32k.sys / win32kfull.sys) is the kernel-mode component of the Windows graphics and windowing subsystem that services GDI and USER calls from user mode. Because it runs in kernel context yet exposes a large syscall surface to unprivileged processes, it has historically been a prime target for local privilege escalation. The root cause here is classified as CWE-284 (Improper Access Control), meaning the component fails to correctly enforce a permission or ownership check on an object or operation, letting a lower-privileged caller reach functionality or objects it should not. The affected CPE set spans Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025, indicating the vulnerable code path is long-lived and present across the modern Windows kernel line.
RemediationAI
Apply the Microsoft security update for CVE-2026-49805 (Patch available per vendor advisory) via Windows Update or WSUS/SCCM for every affected client and server SKU, prioritizing multi-user systems such as Remote Desktop Session Hosts, VDI, and shared workstations where untrusted users execute code. The authoritative per-build fixed versions are listed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49805; consult that advisory for the exact patched build for each OS version rather than assuming a single version number. Where immediate patching is not possible, reduce exposure by limiting the ability of untrusted or standard users to run arbitrary code on affected hosts (application allowlisting such as WDAC/AppLocker) and by monitoring for anomalous local process behavior, though these are compensating controls that do not remove the underlying flaw and can impose administrative overhead. There is no vendor-documented in-product configuration workaround, so patching is the definitive remediation.
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Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
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External POC / Exploit Code
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