The following errata for CentOS-2 have been built and uploaded to the centos mirror:
RHSA-2005:384-01 Important: Mozilla security update
Files available: galeon-1.2.14-1.2.3.i386.rpm mozilla-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-chat-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-devel-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-dom-inspector-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-js-debugger-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-mail-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-nspr-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-nspr-devel-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-nss-1.7.7-1.1.2.1.c2.1.i386.rpm mozilla-nss-devel-1.7.7-1.1.2.1.c2.1.i386.rpm
More details are available from the RedHat web site at https://rhn.redhat.com/errata/rh21as-errata.html
The easy way to make sure you are up to date with all the latest patches is to run: # yum update