CVE-2026-78450: Microsoft Windows 10 1809

High severity, CVSS 8.1. EPSS: 0.7% chance of exploitation in the next 30 days.

Use after free in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over a network.

Affected products

• Microsoft Windows 10 1809: before 10.0.17763.9245 (fixed in 10.0.17763.9245)
• Microsoft Windows Server 2019: before 10.0.17763.9245 (fixed in 10.0.17763.9245)
• Microsoft Windows Server 2022: before 10.0.20348.5622 (fixed in 10.0.20348.5622)
• Microsoft Windows Server 2025: before 10.0.26100.33438 (fixed in 10.0.26100.33438)

Published 2026-09-08. Last modified 2026-09-16.