The C based programs I use most are probably various databases (mysql, postgres, redis, sqlite etc) and the linux kernel. Certainly for the databases they have been rock solid. It's possible to crash them by running the server out of resources of course, but I have never had them outright crash with a malloc problem. The kernel has more bugs perhaps, but that too has been rather stable for me.

C might not be perfect but it's clearly perfectly possible to write stable and secure programs in them.