I guess you are here because of the ShellShock wave and you want to fix your debian squeeze system. No worries, read on.
If you have Debian Lenny, follow this link: http://tar.gz.ro/debian-lenny-bash-shellshock.html

How to upgrade Bash on Debian Squeeze:
1. Replace squeeze with wheezy in /etc/apt/sources.list or just save the current file and overwrite it with the following:

############################################################
################### OFFICIAL DEBIAN REPOS ###################
#############################################################

###### Debian Main Repos
deb http://ftp.debian.org/debian/ wheezy main contrib non-free
deb-src http://ftp.debian.org/debian/ wheezy main contrib non-free

###### Debian Update Repos
deb http://security.debian.org/ wheezy/updates main contrib non-free
deb http://ftp.debian.org/debian/ wheezy-proposed-updates main contrib non-free
deb-src http://security.debian.org/ wheezy/updates main contrib non-free
deb-src http://ftp.debian.org/debian/ wheezy-proposed-updates main contrib non-free

2. Run aptitude update
3. Install only Bash and its dependencies with command apt-get install --only-upgrade bash:

core:dist# apt-get install --only-upgrade bash
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libtinfo5 multiarch-support
Suggested packages:
  bash-doc
The following NEW packages will be installed:
  libtinfo5 multiarch-support
The following packages will be upgraded:
  bash
1 upgraded, 2 newly installed, 0 to remove and 1303 not upgraded.
Need to get 1,927 kB of archives.
After this operation, 1,031 kB of additional disk space will be used.
Do you want to continue [Y/n]? 
Get:1 http://security.debian.org/ wheezy/updates/main multiarch-support amd64 2.13-38+deb7u4 [151 kB]
Get:2 http://ftp.debian.org/debian/ wheezy/main libtinfo5 amd64 5.9-10 [275 kB]
Get:3 http://security.debian.org/ wheezy/updates/main bash amd64 4.2+dfsg-0.1+deb7u3 [1,501 kB]
Fetched 1,927 kB in 0s (3,554 kB/s)                        
[...]
Processing triggers for menu ...

4. Check bash and find out it is no more vulnerable:

core:~# env x='() { :;}; echo Bash is vulnerable!' bash -c "echo PS: this is just a test..."
PS: this is just a test...

4. Put back squeeze in /etc/apt/sources.list (or restore the previously saved file) and run again aptitude update