If you're using CentOS, you can leverage Redhat's spacewalk project. However, this will do more than just track errata. Spacewalk will also inventory your hardware and software, install software, provision servers and take care of some monitoring. If that suits your use-case, then spacewalk could be the option for you.
Steve Meier of the CEFS project has made the process for tracking CentOS errata via spacewalk very easy and free. He provides a parsed errata.xml file generated from the centos-announce mailing lists and the scripts you need to import them in to your spacewalk server.
However, not everyone wants to run spacewalk. There are many reasons this may be the case. If you are one of these people, you're left with tracking the centos-announce mailing list using your own processes.
We'd like to present another option. What if we want to leverage the power of yum to tell us when a package needs to be updated? We can do this by installing the yum-plugin-security package. You're now one step closer, but the CentOS repositories do not come with a updateinfo.xml file that includes the relevant data that the plugin uses.
This is where we got the idea to leverage the CEFS project data and utilize the functionality of the updateinfo.xml file. All we needed to do is convert the errata.xml data in to the appropriate updateinfo.xml format and inject it in to the applicable CentOS repositories.
The following example illustrates how you would go about using this for a CentOS 6 repo. The assumption is that you've set the BUILD_PREFIX=/security and that your CentOS-6-Updates directory lives under /repositories/
wget -q -N -P/security http://cefs.steve-meier.de/errata.latest.xml generate_updateinfo.py /security/errata.latest.xml /usr/bin/modifyrepo /security/updateinfo-6/updateinfo.xml /repositories/CentOS-6-Updates/repodata
Now that your repos have the data they need you can install the yum-plugin-security package and make use of it like so
yum install yum-plugin-security yum security-list Loaded plugins: changelog, fastestmirror, security Loading mirror speeds from cached hostfile CentOS-6-OS | 1.2 kB 00:00 CentOS-6-Updates | 1.2 kB 00:00 CESA_2013__1764 security ruby-188.8.131.522-13.el6.x86_64 CESA_2013__1764 security ruby-irb-184.108.40.2062-13.el6.x86_64 CESA_2013__1764 security ruby-libs-220.127.116.112-13.el6.x86_64 CESA_2013__1764 security ruby-rdoc-18.104.22.1682-13.el6.x86_64 CESA_2013__1806 security samba-client-3.6.9-167.el6_5.x86_64 CESA_2013__1806 security samba-common-3.6.9-167.el6_5.x86_64 CESA_2013__1806 security samba-winbind-3.6.9-167.el6_5.x86_64 CESA_2013__1806 security samba-winbind-clients-3.6.9-167.el6_5.x86_64