CVE-2026-58530 is a Windows Resilient File System (ReFS) heap-based buffer overflow that can lead to remote code execution. Microsoft rates it CVSS v3.1 7.8 (High) with a temporal score of 6.8; the vector is LOCAL, LOW attack complexity, NO privileges required, and USER INTERACTION required. Microsoft states it is not publicly disclosed, not exploited, and exploit code maturity is UNPROVEN. This is a high-severity issue, but the local attack vector and required user interaction reduce enterprise exposure compared with network-reachable vulnerabilities.

Highlights:
- CVSS scores: Base 7.8 - Temporal 6.8
- Exploit status & code maturity: Publicly Disclosed: No; Exploited: No; Exploit Code Maturity: UNPROVEN.
- Impact: Remote Code Execution with HIGH confidentiality, HIGH integrity, and HIGH availability impacts.
- Exploitation likelihood: Exploitation Unlikely; the vector is LOCAL with LOW attack complexity and USER INTERACTION required, which lowers remote enterprise exposure.
- Severity for enterprise: High technical severity, but lower enterprise-wide risk than network-exploitable issues because exploitation is local and requires user interaction.
- Patch status: available

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