Can bash be replaced entirely in OS X?
First, you don't need to do this unless you are are offering web services to the public internet from your Mac. If you are not, wait until there is an official security update from Apple.

However, if you are offering web services, you might want to update.

Official Patch

Apple has released an Official Bash Security Update Here

Checking whether you are vulnerable

First confirm that you are using an outdated bash:

$ which bash
/bin/bash
$ /bin/bash --version
GNU bash, version 3.2.51(1)-release (x86_64-apple-darwin13)
Copyright (C) 2007 Free Software Foundation, Inc.


The most current bash is 4.3.25

If you don't have Xcode installed, you'll need the Xcode command line tools, which can be installed by

$ xcode-select --install


Or from the developer portal.

To install Brew (http://brew.sh):

$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"


Then do:

$ brew doctor


Follow any instructions if there are problems. Many common problems are addressed here.

Then update brew to the latest list of packages:

$ brew update


To get the latest bash 4.3.25:

$ brew install bash


This installs bash into /usr/local/Cellar/bash/4.3.25/bin/bash

The old bash and sh still exists at /bin, so after installing you'll rename the old executables to a new file.

$ sudo mv /bin/bash /bin/bash_old
$ sudo mv /bin/sh /bin/sh_old


If you are very paranoid, you can remove execute permissions on the bash_old

$ sudo chmod a-x /bin/bash_old /bin/sh_old


Then create a symbolic link to the new bash 4.3.25 that brew installed.

$ sudo ln -s /usr/local/Cellar/bash/4.3.25/bin/bash /bin/bash
$ sudo ln -s /usr/local/Cellar/bash/4.3.25/bin/bash /bin/sh


Reboot and it is complete.

A warning — this may break some existing shell scripts that might rely on bash 3.2 or the differences that the Mac sh has over the linux sh. There is a much more sophisticated answer to replacing bash and sh from sources in this post.

In most cases it is best to wait for official updates.