How to repair a hole in exterior concrete foundation

We have had this hole in our exterior foundation for a few years. The way we discovered it was that water was leaking into our basement finished room, and when I looked outside, I discovered this hole in a corner where the porch foundation and the house foundation meet. It is now the size of a peach. We have dealt with it temporarily by covering the whole area with tarp and duct tape, and have never had any water in the basement since then.

My question is, how do we repair a hole that is empty behind it? There is some sort of crawl space underneath the porch (porch is concrete). Here is a picture of the hole:

We are somewhat novices at DIY – I can build furniture fairly easily, but concrete is something new to me. Thanks for your help!