EUVD-2026-43828
GHSA-r887-jmv7-w8rp
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local kernel-driver flaw exploitable by an authenticated low-privileged user with no interaction (AV:L/PR:L/UI:N); kernel code execution yields full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Stack-based buffer overflow in Windows Resilient File System (ReFS) allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Windows Resilient File System (ReFS) allows an authenticated low-privileged user to gain elevated (SYSTEM-level) privileges by triggering a stack-based buffer overflow (CWE-121) in the ReFS driver. The flaw affects a broad range of Windows client and server releases, from Windows 10 1607 through Windows 11 26H1 and Windows Server 2016 through 2025. Microsoft has released a patch; there is no public exploit identified at time of analysis and the CVE is not listed in CISA KEV.
Technical ContextAI
ReFS (Resilient File System) is Microsoft's newer file system designed for large-scale data storage, integrity checking, and resiliency, implemented as a kernel-mode driver. The root cause is CWE-121 (Stack-based Buffer Overflow): the ReFS driver copies attacker-influenced data into a fixed-size stack buffer without adequate bounds checking, corrupting the kernel stack (including saved return addresses or adjacent variables) and enabling control-flow or memory corruption within kernel context. Because ReFS runs in the kernel, a successful overflow yields code execution at the highest privilege level. Per the supplied CPE data, the affected surface spans 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-2026-50318 as the primary fix - Patch available per vendor advisory (Microsoft update guide: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50318); consult that page for the exact KB article and build number matching each affected Windows 10, Windows 11, and Windows Server release, as an exact fix version was not included in the provided data. Prioritize patching hosts that use ReFS volumes (common on storage servers, Storage Spaces Direct, backup targets, and Hyper-V hosts). Where immediate patching is not possible, reduce exposure by limiting interactive and local logon rights to trusted administrators, tightening who can mount or attach removable/ReFS media, and monitoring for local privilege-escalation behavior; note these are only partial compensating controls because any authenticated local user able to interact with an ReFS volume remains a potential attacker, and restricting ReFS use may not be feasible where it backs production storage.
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Same weakness CWE-121 – Stack-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
Leaving vuln.today