EUVD-2026-56684
GHSA-vmq2-279f-4hcf
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local kernel-mode driver exploitation requiring only a standard user session; no network vector, no interaction, full C/I/A impact upon SYSTEM escalation.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Windows Win32K allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation via heap-based buffer overflow in Windows Win32K (win32k.sys) allows a low-privileged local user to achieve full SYSTEM-level control across a broad range of Windows and Windows Server releases. The vulnerability spans Windows 10 1607 through Windows 11 26H1 and Windows Server 2012 through Server 2025, making the attack surface effectively ubiquitous across enterprise environments. No public exploit identified at time of analysis, but vendor-released patches are available via the Microsoft Security Response Center.
Technical ContextAI
Win32K (win32k.sys) is the kernel-mode component of the Windows graphics and windowing subsystem, responsible for processing USER and GDI system calls. CWE-122 (Heap-based Buffer Overflow) identifies the root cause: attacker-controlled input overflows a heap allocation within the Win32K driver, enabling corruption of adjacent kernel heap memory. Because Win32K executes entirely in Ring 0, heap metadata or function pointer corruption at this layer can be leveraged to redirect execution to attacker-controlled shellcode or overwrite security tokens, granting SYSTEM privileges. This class of vulnerability in Win32K has a long exploitation history; CPE-covered products span six major Windows release lines across both client and server SKUs, confirmed by EUVD-2026-56684 data.
RemediationAI
The primary fix is to apply Microsoft's released security update, which patches Win32K across all affected release lines. Target build thresholds by platform: Windows Server 2025 to 10.0.26100.33296, Windows Server 2022 to 10.0.20348.5499, Windows 11 26H1 to 10.0.28000.2704, Windows 11 25H2 to 10.0.26200.9168, Windows 11 24H2 to 10.0.26100.9168, Windows 11 23H2 to 10.0.22631.7517, Windows 10 22H2 and 21H2 to 10.0.19045.7663 or 10.0.19044.7663 respectively, Windows Server 2019 and Windows 10 1809 to 10.0.17763.9115, Windows Server 2016 and Windows 10 1607 to 10.0.14393.9418, and Windows Server 2012 / 2012 R2 to 6.2.9200.26279 or 6.3.9600.23337. Updates are available via Windows Update, WSUS, and the Microsoft Update Catalog. As a compensating control where patching is delayed, defenders should restrict untrusted local user access through application control policies (AppLocker, Windows Defender Application Control) to limit the attacker's ability to invoke Win32K system calls; this reduces exposure but does not eliminate it, since any authenticated local user session is in scope. Prioritize patching on shared multi-user systems (RDP servers, Citrix hosts, VDI), where untrusted users are most likely to have local sessions. Reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62885.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
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