Documenting this in case someone else runs across it. I just had a weird issue where if I ran cd / in my Mac OS X bash shell, the shell closed. It happened if I cd‘ed to any directory outside of my home directory structure.
In my case, I figured it out when I opened a shell within my terminal by running bash and then trying. The bash shell exited with an error: Abort trap: 6. It turns out that something in the system must have changed, and I needed to recompile my homebrew bash.