Bash is the shell, the cmd, the terminal, you need administrator priveleges to do anything, is no enough to get acces to it, you could launch it but you still need to be root in order to gain control of the system, so if your system doesn't have a root password . . . you deserve whatever happens to you
Also in Linux the time elapsed beteween discovering a security risk and the development and launching of the patch to fix it is sometimes no longer than two hours, although it could take more deppending on the dificulty to patch it.
Don't know about Mac but on windows you are lucky if a third party (Antivirus, etc.) does something about it in a short period of time, here numbers count and there are thousands of people contributing to linux development.
What me worry?