After applying the latest bash RPM listed at http://lists.CentOS.org/pipermail/CentOS-announce/2014-September/020594.html :
The fixed RPM (bash-3.2-33.el5_10.4.x86_64.rpm) DOES work just fine on CentOS 5.10. However, it DOES NOT work on CentOS 5.4. That is, bash runs fine, but IS STILL VULNERABLE TO SHELLSHOCK!
Scary screenie at: http://i.imgur.com/yR7sBjV.png
It looks like the released RPM somehow behaves DIFFERENTLY on 5.4 as opposed to 5.10.
This has been validated by one of my coworkers; it’s apparently not just me.