EUVD-2026-43997
GHSA-vh8f-cgr8-9hm9
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local privilege escalation requiring an existing low-privileged account (AV:L, PR:L), low complexity with no user interaction, yielding full SYSTEM control (C/I/A:H) within an unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
5DescriptionNVD
Use after free in Windows Hyper-V allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Windows Hyper-V (affecting Windows 10, Windows 11, and Windows Server 2019 through 2025) allows an authenticated local attacker to elevate to SYSTEM by exploiting a use-after-free (CWE-416) memory corruption condition in the hypervisor stack. Microsoft reported the issue and has shipped fixes; there is no public exploit identified at time of analysis, and the low EPSS score (0.20%, 10th percentile) plus CISA SSVC 'Exploitation: none' indicate no observed exploitation yet. The total technical impact (full C/I/A compromise) makes it a meaningful patch priority on any Hyper-V-enabled host despite the local attack vector.
Technical ContextAI
Hyper-V is Microsoft's Type-1 (bare-metal) hypervisor built into Windows client and server SKUs, providing hardware virtualization, VM isolation, and virtualization-based security (VBS) features. The root cause is a use-after-free (CWE-416): code paths within the Hyper-V component retain and dereference a pointer to memory that has already been freed, letting an attacker who can control heap allocation/reuse corrupt kernel-mode objects. The CPE data confirms the affected surface spans Windows 10 (1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2019/2022/2025 including Server Core installations, meaning any deployment with the Hyper-V role or virtualization components enabled is in scope. Because Hyper-V code runs at a high privilege boundary, successful reuse of a dangling pointer can be leveraged to execute attacker-controlled logic in the kernel/hypervisor context and defeat the isolation guarantees Hyper-V normally enforces.
RemediationAI
Apply the Microsoft security update for your specific Windows build as the primary fix: Vendor-released patch confirmed per MSRC (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54129). Update to at least the following fixed builds - Windows Server 2019 / Windows 10 1809 to 10.0.17763.9020, Windows 10 21H2 to 10.0.19044.7548, Windows 10 22H2 to 10.0.19045.7548, Windows Server 2022 to 10.0.20348.5386, Windows Server 2025 to 10.0.26100.33158, Windows 11 24H2 to 10.0.26100.8875, Windows 11 25H2 to 10.0.26200.8875, and Windows 11 26H1 to 10.0.28000.2269. Where immediate patching is not possible, reduce exposure by limiting who holds interactive/local logon and low-privileged accounts on Hyper-V hosts, since exploitation requires local access with PR:L; on systems that do not actually require virtualization, disabling the Hyper-V role/feature removes the vulnerable surface, though this will break any running VMs, WSL2, containers, and VBS-dependent security features and should only be done on hosts where those are unused. Prioritize multi-tenant and VM-hosting servers where untrusted low-privileged users or guest workloads are present.
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External POC / Exploit Code
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