CVE-2026-78449: CWE-416: Use After Free in Microsoft Windows 10 Version 1607

CVE-2026-78449 is a use-after-free vulnerability (CWE-416) in the Reliable Multicast Transport Driver (RMCAST) of Microsoft Windows 10 Version 1607 and other affected versions. This vulnerability enables remote code execution by an unauthenticated attacker over a network. The flaw affects multiple Windows 10 and Windows Server builds, specifically versions from 6.2.9200.0 up to but not including certain patched builds (e.g., <10.0.14393.9512, <10.0.17763.9245, etc.). Microsoft has published an official security update to fix this vulnerability. The CVSS v3.1 base score is 8.1, indicating high severity, with network attack vector, high impact on confidentiality, integrity, and availability, and requiring no privileges or user interaction.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code remotely on affected systems without requiring user interaction or privileges. This could lead to full system compromise, including control over confidentiality, integrity, and availability of the system. The vulnerability affects multiple Windows 10 and Windows Server versions, potentially impacting a wide range of enterprise and personal systems.

Microsoft has released official security updates that address this vulnerability. It is strongly recommended to apply the provided patches from the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78449. No additional mitigation steps are required beyond applying the official fix.