CVE-2026-50399 is a Windows Kernel Elevation of Privilege vulnerability described as an out-of-bounds read. Microsoft rates it CVSS v3.1 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 unchanged scope and HIGH confidentiality, integrity, and availability impacts. Microsoft says it is not publicly disclosed, not exploited, and exploit code maturity is unproven. Successful exploitation could grant SYSTEM privileges. Because the attack is local-only, enterprise risk is mainly for systems where an attacker already has local access or can run code on the host.

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; HIGH confidentiality, HIGH integrity, and HIGH availability impact; attacker can gain SYSTEM privileges
- Exploitation likelihood: Exploitation Less Likely; LOCAL vector with LOW attack complexity, LOW privileges required, and NO user interaction
- Severity for enterprise: High severity by CVSS, but lower exposure risk than remote vulnerabilities because exploitation requires local access; highest concern is on systems where untrusted local users, code execution, or shared access is present
- Patch status: available; customer action required

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