I'm late but I've found the main culprit is "ucrtbased.dll". I'm on Windows 7 SP1 x64, Qt 5.9.2 with Visual Studio Build Tools 2015 (v14.0.25420.1) and Windows 8.1 SDK with MS Debugger Tools (CDB) installed. I didn’t install Windows 10 SDK. The Release Configuration builds are without any issue but the Debug Configuration exhibits the same crash behavior. The fix is simple. The normal install of Visual Studio Build Tools 2015 with Win8.1 SDK places "ucrtbased.dll" in "C:\Program Files (x86)\Windows Kits\10\bin\x64\ucrt" for 64-bit and "..\x86\ucrt" for 32-bit builds - even the Windows 10 SDK is not installed. If these are included in system path, or copied to the Qt's current project build folder, the issue is simply resolved.