EUVD-2026-43839
GHSA-jmvx-6p58-9955
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local authenticated attacker (AV:L, PR:L) with no user interaction; high complexity reflects a likely race condition, and successful EoP grants full SYSTEM control (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
Privilege escalation in the Windows Win32K kernel-mode subsystem lets an already-authenticated local user gain SYSTEM-level control across a broad range of Windows client and server releases (Windows 10 1607 through Windows 11 26H1, and Windows Server 2012 through Server 2025). Rooted in improper access control (CWE-284), successful exploitation yields full confidentiality, integrity, and availability impact on the host. There is no public exploit identified at time of analysis and the CVSS vector's high attack complexity (AC:H) tempers the practical risk.
Technical ContextAI
Win32K is the kernel-mode component (win32k.sys and related drivers) that implements the Windows GUI, window management, and the graphics device interface, and it has historically been one of the largest local kernel attack surfaces because it exposes numerous system calls reachable from low-privileged user contexts. The root cause is classified as CWE-284 (Improper Access Control), meaning the driver fails to correctly enforce authorization on an object or operation, allowing a caller to act with privileges it should not hold. The CPE data confirms the flaw spans the Win32K code shared across Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025, indicating a long-lived code path common to both client and server SKUs including Server Core installations.
RemediationAI
Patch available per vendor advisory: apply the Microsoft security update for CVE-2026-50325 via the MSRC update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50325, selecting the cumulative update matching each affected build (Windows 10 1607/1809/21H2/22H2, Windows 11 24H2/25H2/26H1, and Windows Server 2012 through 2025 including Server Core). Exact per-build KB/version numbers should be taken from the MSRC page and are not restated here to avoid inventing version numbers. Because exploitation requires an authenticated local foothold, meaningful compensating controls until patching include enforcing least privilege and removing unnecessary interactive/RDP logon rights on servers, restricting local logon on domain controllers and high-value hosts, and monitoring for unexpected SYSTEM-level process spawns or token manipulation; note these controls reduce the pool of potential attackers but do not close the underlying Win32K flaw, so they are stopgaps rather than substitutes for the update.
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Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today