EUVD-2026-44014
GHSA-7mf4-r8f9-vvqp
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Requires existing low-privileged local access to reach the ReFS driver (AV:L/PR:L), low complexity, no interaction, and kernel code execution yields full C/I/A impact within an unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Integer overflow or wraparound in Windows Resilient File System (ReFS) allows an authorized attacker to execute code locally.
AnalysisAI
Local privilege escalation to code execution in the Windows Resilient File System (ReFS) driver affects a broad range of Windows 10/11 and Windows Server 2016 through 2025 releases, where an integer overflow (CWE-190) in filesystem processing lets an already-authenticated local user run arbitrary code in an elevated context. The CVSS 3.1 vector (AV:L/PR:L) confirms low-privileged local access is required rather than remote exploitation, and there is no public exploit identified at time of analysis. Microsoft has released a patch via MSRC.
Technical ContextAI
ReFS (Resilient File System) is Microsoft's newer copy-on-write filesystem used primarily on Windows Server for large-volume, integrity-checked storage (Storage Spaces, Hyper-V VHDs, backup targets) and available on client Windows. The weakness is CWE-190, an integer overflow or wraparound: a computed size or index value in the kernel-mode ReFS driver exceeds the storage width of its integer type and wraps to a small or negative value, which then feeds an undersized allocation or an out-of-bounds access - the tags also flag this as a resulting buffer overflow. Because ReFS parsing runs in kernel context, a successful overflow yields execution at a privilege level above the invoking user. CPE data scopes this to Microsoft Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2016, 2019, 2022 and 2025 including Server Core installations.
RemediationAI
Apply the Microsoft security update for CVE-2026-54109 - Vendor-released patch: available from vendor via the monthly cumulative update for each affected OS; consult https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54109 for the exact fixed build per Windows 10/11 and Server SKU and deploy it through Windows Update, WSUS or your patch-management tooling. Because the flaw is local and requires ReFS access, an interim compensating control on servers is to restrict standard-user access to ReFS volumes and limit interactive/standard-user logon on systems where ReFS is used only for backend storage (e.g. Hyper-V or backup hosts) - this narrows who can invoke the vulnerable driver but does not remove the flaw and can disrupt legitimate application access to those volumes. Where ReFS is not required, using NTFS avoids exposure of this specific driver path. Patching remains the only complete fix; the workarounds only reduce reachable attack surface.
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Same weakness CWE-190 – Integer Overflow or Wraparound
View allSame technique Buffer Overflow
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External POC / Exploit Code
Leaving vuln.today