There's also a solution of updating your sources.list to the newest one and then using apt-get to upgrade only bash. It's really quick and I've written an article about it. Here's what you basically do:
Upgrade to latest Ubuntu 'trusty' apt-get repositories (you might also have to change old-repositories.ubuntu.com URLs if you use them, check linked article):
sudo sed -i 's/YOUR_OS_CODENAME/trusty/g' /etc/apt/sources.listUpgrade bash / apply fix:
sudo apt-get updatesudo apt-get install --only-upgrade bashAnd possibly change back apt-get repositories.