MSBuild error MSB8040

Spectre-mitigated libraries are required for this project.

This error occurs when using Spectre-mitigated libraries is requested (C/C++ > Spectre Mitigation isn't set to Disabled), but Spectre-mitigated libraries aren't installed.

To fix the error, first decide if you want Spectre mitigation. You can read about Spectre mitigation at the page for the /Qspectre compiler option. If you don't want Spectre mitigation, make sure it's disabled. For command-line builds, check that you're not using the /Qspectre compiler option or its variants /Qspectre-load and /Qspectre-load-cf. To disable it in the Visual Studio IDE, open Properties for your projects, and in the Configuration Properties > C/C++ > Code Generation property page, set the Spectre Mitigations property to Disabled.

If you want Spectre mitigation, make sure that the right compiler and library components with support for Spectre mitigation are installed. In the Visual Studio Installer, choose Modify and then choose Individual Components, search for "Spectre v14.2," and in the Compiler, build tools and runtime section, make sure that MSVC v142… Spectre-mitigated libs are selected for all architectures that you're building for. If you're using ATL or MFC, make sure that the libraries, such as C++ MFC for latest v142 build tools with Spectre Mitigations (or the appropriate version for your toolset) are also selected for all the architectures you're building for.

Also, to enable Spectre mitigations, make sure that you're using one of the /Qspectre compiler options. To set this property in the Visual Studio IDE, open Properties for your projects, and in the Configuration Properties > C/C++ > Code Generation property page, set the Spectre Mitigations property to Enabled, or All loads for /Qspectre-load, or All Control Flow Loads for /Qspectre-load-cf.

For more information, see Spectre mitigations in MFC.