EUVD-2026-56586
GHSA-mv9j-3963-rw7w
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local-only exploitation requiring a standard authenticated user session; full C/I/A assigned because successful privilege escalation to SYSTEM yields complete control of the local system with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
7DescriptionNVD
Heap-based buffer overflow in Windows DNS allows an authorized attacker to elevate privileges locally.
AnalysisAI
Heap-based buffer overflow in the Windows DNS component enables a locally authenticated low-privileged attacker to escalate privileges to SYSTEM across a broad range of Windows releases, from Windows 10 version 1607 through Windows 11 26H1 and Windows Server 2012 through Server 2025. The CVSS 3.1 score of 7.8 reflects low attack complexity and full confidentiality, integrity, and availability impact once local access is obtained, with no user interaction required. No public exploit code or active exploitation has been identified at time of analysis, and a vendor-released patch is available via the Microsoft Security Response Center.
Technical ContextAI
CWE-122 identifies a heap-based buffer overflow, which occurs when data written to a dynamically allocated heap buffer exceeds its allocated capacity, corrupting adjacent memory regions. In the Windows DNS component (the DNS client or server service), such an overflow can overwrite heap metadata, vtable pointers, or function pointers, enabling an attacker to redirect code execution to attacker-controlled code. CPE data confirms impact across x86, x64, and ARM64 builds of Windows 10 versions 1607, 1809, 21H2, and 22H2, and tags extend coverage to Windows 11 versions 23H2 through 26H1 and Windows Server 2012 through Server 2025. Because the vulnerability resides within a privileged OS component handling DNS operations, successful exploitation provides a direct path from a low-privilege user session to SYSTEM-level control without requiring any scope change, consistent with the CVSS S:U rating.
RemediationAI
Microsoft has released cumulative updates addressing this vulnerability for all affected Windows versions; organizations should apply the relevant update immediately via Windows Update or WSUS. Specific fixed build targets confirmed by EUVD data 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 and Server 2025 to 10.0.26100.33296 or later, Windows 11 25H2 to 10.0.26200.9168 or later, Windows 11 26H1 to 10.0.28000.2704 or later, Server 2022 to 10.0.20348.5499 or later, Server 2012 to 6.2.9200.26279 or later, and Server 2012 R2 to 6.3.9600.23337 or later. Full advisory details are available at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70304. Where immediate patching is operationally infeasible, restrict local interactive logon and Remote Desktop access to the minimum required set of trusted accounts, and audit local group memberships to remove unnecessary low-privileged accounts; note that these controls reduce the attacker pool but do not eliminate the vulnerability.
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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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