CVE-2026-50318 - Windows Resilient File System (ReFS) Elevation of Privilege Vulnerability - is a stack-based buffer overflow in ReFS that can be used for elevation of privilege. The CVSS v3.1 base score is 7.8 (High) with a temporal score of 6.8; the vector is LOCAL, LOW attack complexity, LOW privileges required, and NO user interaction, with HIGH impacts to confidentiality, integrity, and availability. Microsoft lists exploitation as unlikely, with no public disclosure and no known exploitation, and exploit code maturity is UNPROVEN. Because this is a local vulnerability, enterprise risk is primarily on systems where a low-privilege local attacker can run code.

Highlights:
- CVSS scores: Base 7.8 - Temporal 6.8
- Exploit status & code maturity: Publicly Disclosed: No; Exploited: No; Exploit Code Maturity: UNPROVEN.
- Impact: Elevation of Privilege with HIGH confidentiality, integrity, and availability impacts.
- Exploitation likelihood: Exploitation Unlikely; the LOCAL vector means it requires local access and is not a network-reachable attack.
- Severity for enterprise: High technical severity, but lower risk for internet-facing services because exploitation is local-only. Higher concern applies to shared Windows systems where untrusted local code or users may be present.
- Patch status: available; customer action is required.

Affected systems:
- Windows 10 1607
- Windows 10 1809
- Windows 10 21H2
- Windows 10 22H2
- Windows 11 24H2
- Windows 11 25H2
- Windows 11 26H1
- Windows 11 unspecified
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
- Windows Server 2025