Critical Remote Code Execution Flaw in Microsoft Windows TCP/IP Stack (CVE-2026-2316)

Microsoft has issued an urgent security advisory for CVE-2026-2316, a critical remote code execution (RCE) vulnerability in the Windows TCP/IP stack. Unauthenticated attackers can exploit this flaw by sending specially crafted network packets to affected systems. Successful exploitation grants full system control without user interaction.

Affected Products:

• Windows 10 versions 22H2 and earlier
• Windows 11 versions 23H2 and earlier
• Windows Server 2019
• Windows Server 2022

This vulnerability carries a CVSS v3.1 score of 9.8 (Critical). The attack vector is network-based, requiring no privileges or user action. Exploits are likely due to the simplicity of packet transmission and the prevalence of vulnerable systems.

Microsoft confirmed the vulnerability resides in how the TCP/IP driver (tcpip.sys) processes IPv6 fragmented packets. Malicious payloads bypass memory protections when reassembling packet fragments. This allows arbitrary code execution in kernel mode.

Mitigation Steps:

1. Apply Microsoft's security update immediately via Windows Update or the Microsoft Update Catalog
2. Block inbound IPv6 traffic at network perimeter devices
3. Disable IPv6 if not operationally required

Microsoft's advisory confirms patches are available for all supported Windows versions through the Security Update Guide. Organizations should prioritize patching internet-facing systems within 24 hours. Microsoft Threat Intelligence has detected limited targeted attacks leveraging this vulnerability.

System administrators should verify patch installation using the KB5036893 update identifier. Unsupported systems require upgrading to maintained Windows versions. Microsoft recommends enabling automatic updates for enterprise environments via Windows Server Update Services.

The disclosure timeline:

• April 2, 2026: Vulnerability reported to Microsoft
• April 9, 2026: Patch released (Patch Tuesday)
• April 10, 2026: Public advisory published

This marks the third critical TCP/IP stack vulnerability in 12 months. Network administrators should review firewall rules and segment critical infrastructure.