Microsoft confirms a critical-severity vulnerability (CVE-2026-20819) in Windows networking components allowing unauthenticated remote code execution. Affected systems include Windows 10, Windows 11, and Windows Server 2022.
A critical security flaw in Microsoft Windows enables attackers to execute malicious code remotely without authentication. Tracked as CVE-2026-20819, this vulnerability carries a CVSS v3.1 severity score of 9.8 (Critical). Successful exploitation grants attackers SYSTEM-level privileges on compromised devices.
Impacted products include Windows 10 versions 22H2 and later, Windows 11 all versions, and Windows Server 2022. The vulnerability resides in the Windows TCP/IP protocol stack. Attackers can trigger the flaw by sending specially crafted network packets to exposed systems.
Microsoft confirmed the vulnerability allows remote code execution without user interaction. Systems with network exposure are especially vulnerable. Microsoft released patches addressing CVE-2026-20819 on July 9, 2026. These updates are distributed through Windows Update and the Microsoft Update Catalog.
Administrators must apply security updates immediately. Unpatched systems should disable vulnerable TCP/IP features using PowerShell commands. Microsoft recommends blocking ports 135-139 and 445 at network boundaries as temporary mitigation.
The vulnerability was reported to Microsoft through coordinated disclosure on May 15, 2026.
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