EUVD-2026-44260
GHSA-6qff-8m44-xgj8
Severity by source
AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Network-reachable NFS with race-condition timing gives AV:N/AC:H, an authenticated NFS user gives PR:L, and privilege elevation yields full C:H/I:H/A:H within an unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Time-of-check time-of-use (toctou) race condition in Windows Network File System allows an authorized attacker to elevate privileges over a network.
AnalysisAI
Elevation of privilege in the Windows Network File System (NFS) component affects a broad range of Microsoft platforms - Windows 10 (1607 through 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025 - where an authorized attacker can win a time-of-check/time-of-use (TOCTOU) race condition over the network to gain higher privileges. The CVSS 3.1 vector (AV:N/AC:H/PR:L) indicates a network-reachable but high-complexity flaw requiring low-level existing privileges, with full high impact to confidentiality, integrity and availability. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the target to have the Windows Server for NFS role (or NFS handling) enabled and reachable - this is an optional, non-default Windows feature, which is the primary limiting factor. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Signals are moderate and internally consistent for a serious but not trivially exploitable issue. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who already holds low-privilege authenticated access as an NFS client repeatedly issues concurrent, precisely timed file operations against a Windows Server for NFS export, aiming to swap a file or its state between the service's permission check and its subsequent use. On a successful race window they cross a privilege boundary to obtain elevated rights (and potentially read/modify protected data). … |
| Remediation | Apply the Microsoft security update for CVE-2026-56648 for each affected OS build; the patch is available per the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56648, which provides the exact fixed build numbers per platform (Vendor-released patch: see MSRC update guide - no single global version applies across all builds). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Windows systems running NFS (Windows 10 versions 1607-22H2, Windows 11 versions 24H2/25H2/26H1, and Windows Server 2012-2025) and categorize by business criticality. …
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