Microsoft Warns of Critical Windows Vulnerability CVE-2026-3805

Microsoft has released an emergency security advisory for CVE-2026-3805, a critical vulnerability in Windows operating systems that allows attackers to execute malicious code remotely without requiring authentication. The vulnerability affects Windows 10, Windows 11, and Windows Server versions 2019 through 2025.

The flaw exists in the Windows Remote Procedure Call (RPC) service, a core component that enables communication between processes on networked computers. Attackers can exploit this vulnerability by sending specially crafted network packets to vulnerable systems, potentially gaining complete control over affected machines.

Microsoft rates the severity as "Critical" with a CVSS score of 9.8 out of 10. The company warns that exploitation could lead to malware installation, data theft, account creation, and complete system compromise.

Affected Products:

• Windows 10 (all versions)
• Windows 11 (all versions)
• Windows Server 2019
• Windows Server 2022
• Windows Server 2025

Mitigation Steps:

1. Apply security updates immediately through Windows Update
2. Enable Windows Defender Firewall to block unauthorized RPC traffic
3. Restrict network access to RPC endpoints
4. Monitor network traffic for suspicious RPC activity
5. Consider disabling unnecessary RPC services

The vulnerability was discovered by Microsoft's internal security team during routine security audits. No active exploitation has been reported in the wild as of publication, but Microsoft urges immediate patching given the severity and potential impact.

Organizations should prioritize patching critical infrastructure and systems exposed to the internet. Microsoft has also released detailed technical guidance for enterprise customers through the Microsoft Security Response Center.

For more information, visit the official Microsoft Security Update Guide at https://msrc-blog.microsoft.com or contact Microsoft Support for enterprise assistance.