EUVD-2026-44311
GHSA-mjpw-8r5p-rmgp
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local privilege escalation needing prior low-privileged code execution (AV:L, PR:L), no user interaction, and a use-after-free yielding SYSTEM-level full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows Win32K allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Win32K kernel-mode subsystem allows an authenticated attacker to elevate to SYSTEM by exploiting a use-after-free (CWE-416) memory-corruption condition. The flaw affects a broad range of supported Windows client and server releases (Windows 10 1607 through Windows 11 26H1, and Windows Server 2016 through 2025). Reported by Microsoft with a patch available; there is no public exploit identified at time of analysis and it is not listed in CISA KEV.
Technical ContextAI
Win32K (win32k.sys / win32kfull.sys) is the kernel-mode component that implements the Windows GUI subsystem, window manager, and GDI, running in the kernel and reachable from user mode through a large syscall surface - historically one of the most exploited local attack surfaces on Windows. The root cause is CWE-416 Use After Free: an object is freed while a dangling reference remains, and subsequent use of that stale pointer (often after attacker-controlled reallocation of the freed slot) corrupts kernel memory. Successful control of the reclaimed allocation typically yields an arbitrary read/write or control-flow hijack in ring 0, translating to full SYSTEM privileges. The CPE set confirms the affected components are Microsoft Windows 10 (1607/1809/21H2/22H2), Windows 11 (24H2/25H2/26H1), and Windows Server 2016/2019 (including Server Core), with tags additionally naming Server 2022 and 2025.
RemediationAI
Apply the Microsoft security update for CVE-2026-58632 (Patch available per vendor advisory) via the Microsoft Update Guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58632, which lists the exact patched build/KB for each affected release - this is the primary and recommended fix. No exact fixed version string was included in the input data, so consult the MSRC page for the specific KB per OS version and deploy through Windows Update, WSUS, or your patch-management tooling. Because Win32K flaws require local code execution to exploit, meaningful compensating controls while patching is scheduled include restricting the ability of untrusted users to run arbitrary code on the host (application control such as WDAC/AppLocker, least-privilege user accounts, removing local admin where feasible) and on multi-user or terminal-server systems limiting interactive logon; on server roles where the GUI subsystem is unnecessary, Server Core installations reduce but do not eliminate the Win32K surface. These controls reduce the pool of principals who can trigger the bug but do not remove the vulnerable code, so patching remains mandatory.
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Same weakness CWE-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today