CVE-2026-50309 is a Windows NTFS heap-based buffer overflow that Microsoft classifies as a Remote Code Execution vulnerability. The CVSS v3.1 base score is 7.8 (High) with a temporal score of 6.8; the vector is local attack only, with low attack complexity, low privileges required, and no user interaction. Microsoft lists the exploit status as not publicly disclosed and not exploited, with exploit code maturity unproven. Although the impact is remote code execution with high confidentiality, integrity, and availability impact, the local attack vector makes this lower risk for internet-facing exposure than a network-reachable RCE.

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, integrity, and availability impacts.
- Exploitation likelihood: Exploitation Less Likely; the vector is LOCAL, with LOW attack complexity, LOW privileges required, and NO user interaction.
- Severity for enterprise: High technical severity, but real-world enterprise risk is reduced by the local-only attack vector; this is more relevant where untrusted local code or users can run on affected Windows systems.
- 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 2012
- Windows Server 2012 R2
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
- Windows Server 2025