EUVD-2026-43874
GHSA-x4m3-34g5-88j8
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local low-privileged attacker (AV:L/PR:L) triggers a kernel-mode heap overflow with no user interaction and low complexity, yielding SYSTEM-level full CIA impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Heap-based buffer overflow in Windows Resilient File System (ReFS) allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Windows Resilient File System (ReFS) driver allows an authenticated attacker to run code with SYSTEM-level privileges by triggering a heap-based buffer overflow. The flaw (CVSS 7.8) affects a broad range of Windows 10, Windows 11, and Windows Server 2016-2025 builds and carries high confidentiality, integrity, and availability impact. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already possess authenticated low-privileged local code execution on the target (CVSS PR:L, AV:L), and the host must have the Resilient File System (ReFS) component reachable - realistically a mounted or mountable ReFS volume, or the ability to supply/attach ReFS-formatted media that the vulnerable driver parses. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, score 7.8) describes a locally exploitable, low-complexity elevation-of-privilege bug requiring only low existing privileges and no user interaction, with full CIA impact on the host - a classic and highly valuable local EoP primitive for post-compromise chaining. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who already has a low-privileged foothold on a Windows host - for example through phishing, a compromised service account, or a low-integrity process - invokes a crafted ReFS file-system operation (or mounts a maliciously formatted ReFS volume) that overflows a kernel heap buffer, corrupts adjacent kernel objects, and escalates to SYSTEM. Because the vector is local with low complexity and no user interaction, this is a reliable post-exploitation privilege-escalation step rather than an initial-access vector; no public exploit was identified at time of analysis. |
| Remediation | Apply the Microsoft security update for CVE-2026-50407 (Patch available per vendor advisory; consult the MSRC guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50407 for the exact fixed build number for each affected SKU, as the input does not provide a single fix version). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Conduct an inventory of all Windows 10, Windows 11, and Windows Server 2016-2025 systems to quantify exposure and prioritize by business criticality and user privilege levels. …
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External POC / Exploit Code
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