EUVD-2026-56634
GHSA-h7hq-xfr6-p8j2
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector confirmed by Win32K kernel context; PR:L required as attacker must run code as an authenticated low-privileged user; full C/I/A impact reflects SYSTEM-level privilege escalation with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Use after free in Windows Win32K allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation via use-after-free in the Windows Win32K kernel subsystem affects a broad spectrum of Windows client and server releases, from Windows Server 2012 through Windows 11 25H2. An authenticated local attacker can exploit this flaw with low complexity and no user interaction to achieve full SYSTEM-level privileges (C:H/I:H/A:H per CVSS). No public exploit has been identified at time of analysis, but the low-complexity local exploitation profile - combined with the near-universal deployment footprint of Windows - makes this a high-priority patch for both endpoint and server environments.
Technical ContextAI
Win32K is the kernel-mode component (win32k.sys) of the Windows graphical subsystem responsible for managing windows, menus, GDI objects, and display rendering. CWE-416 (Use After Free) indicates that the vulnerability arises when Win32K accesses a memory object after it has been freed and potentially reclaimed, allowing an attacker who controls the heap layout to corrupt kernel data structures or redirect execution flow. Because Win32K operates at ring-0 (kernel privilege level), a successful exploitation directly yields SYSTEM-level access. The CVSS vector AV:L is consistent with Win32K's kernel-mode, locally-invocable attack surface: any authenticated user process can issue Win32 API or GUI-related system calls to trigger the flaw. Notably, even Windows Server Core installations - which lack a full GUI shell - expose the Win32K subsystem and are listed as affected, indicating the vulnerable code path is not solely GUI-dependent.
RemediationAI
Apply Microsoft's security update immediately via Windows Update, WSUS, or Microsoft Update Catalog. Specific patched build targets confirmed by EUVD data are: Windows Server 2019 and Windows 10 1809 to 10.0.17763.9115; Windows 10 21H2 to 10.0.19044.7663; Windows 10 22H2 to 10.0.19045.7663; Windows 11 23H2 to 10.0.22631.7517; Windows 11 24H2 and 25H2 to 10.0.26100.9168; Windows 11 26H1 to 10.0.28000.2704; Windows Server 2012 to 6.2.9200.26279; Windows Server 2012 R2 to 6.3.9600.23337; Windows Server 2016 to 10.0.14393.9418; Windows Server 2022 to 10.0.20348.5499; Windows Server 2025 to 10.0.26100.33296. These build numbers should be cross-referenced against the authoritative advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62711 before deployment. Where immediate patching is not feasible, apply compensating controls: restrict interactive local logon rights to only necessary accounts using Group Policy (User Rights Assignment > 'Allow log on locally'), as this raises the bar for an attacker needing an authenticated session. Deploy Windows Defender Application Control (WDAC) or AppLocker policies to prevent execution of untrusted binaries, which limits the code an attacker could use to trigger the vulnerability - however, this does not protect against a compromised legitimate process. Neither compensating control eliminates the risk and patching remains the only complete remediation.
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Same weakness CWE-416 – Use After Free
View allSame technique Denial Of Service
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External POC / Exploit Code
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