EUVD-2026-56353
GHSA-v73q-4q7g-65x5
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AV:L confirmed by local-only execution; PR:L because standard user credentials are sufficient; full C/I/A from SYSTEM-level privilege escalation with no scope change.
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 in Windows Win32K via a heap-based buffer overflow enables a locally authenticated attacker to gain SYSTEM-level access across a broad range of Microsoft operating systems from Windows Server 2012 through Windows 11 26H1 and Windows Server 2025. The flaw (CWE-122) requires only standard user privileges and no user interaction, making post-compromise escalation straightforward for any attacker who has already obtained local access. No public exploit has been identified at time of analysis, but the Microsoft Security Response Center has issued a patch and the wide affected product surface warrants urgent remediation.
Technical ContextAI
Win32K (win32k.sys) is the kernel-mode component of the Windows graphics subsystem, handling window management, USER objects, and GDI rendering primitives. A heap-based buffer overflow (CWE-122) occurs when a heap-allocated buffer is written beyond its allocated boundary, corrupting adjacent memory. In the Win32K kernel driver context, such corruption can overwrite sensitive kernel data structures - such as object headers, function pointers, or privilege tokens - enabling an attacker to redirect kernel execution or manipulate the process token to escalate to SYSTEM. Because Win32K services user-mode API calls from all GUI-capable processes, it is reachable from standard unprivileged user accounts via documented Windows API calls. The CVSS vector AV:L/AC:L/PR:L/UI:N is consistent with a locally exploitable kernel graphics driver flaw triggered through crafted syscall sequences, requiring no special configuration.
RemediationAI
Apply the Microsoft security update for CVE-2026-62712 via Windows Update, WSUS, or Microsoft Update Catalog. Fixed build thresholds by product are: Windows 10 1607 and Server 2016 to build 10.0.14393.9418 or later; Windows 10 1809 and Server 2019 to 10.0.17763.9115 or later; Windows 10 21H2 to 10.0.19044.7663 or later; Windows 10 22H2 to 10.0.19045.7663 or later; Windows 11 23H2 to 10.0.22631.7517 or later; Windows 11 24H2 to 10.0.26100.9168 or later; Windows 11 25H2 to 10.0.26200.9168 or later; Windows 11 26H1 to 10.0.28000.2704 or later; Server 2012 to 6.2.9200.26279 or later; Server 2012 R2 to 6.3.9600.23337 or later; Server 2022 to 10.0.20348.5499 or later; Server 2025 to 10.0.26100.33296 or later. Full advisory details are at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62712. Where immediate patching is not feasible, reducing the attack surface by restricting interactive local logon rights via Group Policy (deny local logon to non-administrative accounts on sensitive systems) limits the pool of potential attackers, though this does not eliminate risk from already-authenticated standard users. Note that Windows Server Core installations that disable the full graphical shell may reduce but do not eliminate Win32K attack surface, as Server Core variants are listed as affected in the EUVD data.
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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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