kb5127216

KB5127216 is a Windows 11 Setup Dynamic Update that Microsoft released on September 22, 2026 for all editions of Windows 11 versions 24H2 and 25H2. It addresses security vulnerabilities in Windows Setup binaries and other files used during feature updates, and it supersedes KB5126056, which had shipped only two weeks earlier. Windows Update delivers it automatically. The organizations most affected are those that build Windows 11 installation media or run feature upgrades through WSUS or offline images, since this is the package their media and upgrade workflows should now carry. Microsoft has not disclosed which specific vulnerabilities the update fixes.