CVE-2026-50407 is a Windows Resilient File System (ReFS) elevation of privilege vulnerability caused by a heap-based buffer overflow. It has a CVSS v3.1 base score of 7.8 (High) and a temporal score of 6.8, with a local attack vector, low attack complexity, low privileges required, and no user interaction. Microsoft reports no public disclosure and no known exploitation, with exploit code maturity unproven. Because exploitation requires local access, the enterprise risk is lower for internet-facing services than for systems where untrusted local users or code may be present, but successful exploitation could grant high-impact privilege escalation on affected Windows systems.

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, HIGH integrity, and HIGH availability impacts.
- Exploitation likelihood: Exploitation Less Likely; local vector, LOW attack complexity, LOW privileges required, and NO user interaction.
- Severity for enterprise: High-severity local privilege escalation; more relevant on shared endpoints, servers, or systems with untrusted local access than on network-exposed services.
- Patch status: available; customer action 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