This servicing release was part of the .NET Core 2.1.5 release. It is versioned on NuGet and tagged here are 2.1.4 because EF Core did not make any changes for one of the .NET Core 2.1.x releases. (Going forward we will instead bump up all the versions so that they align.)
The issues fixed in this release can be found in the 2.1.5 milestone