https://rhn.redhat.com/errata/RHSA-2005-043.html refers

updated files :-

updates/i386/RPMS/kernel-2.4.21-27.0.2.EL.athlon.rpm
updates/i386/RPMS/kernel-2.4.21-27.0.2.EL.i586.rpm
updates/i386/RPMS/kernel-2.4.21-27.0.2.EL.i686.rpm
updates/i386/RPMS/kernel-2.4.21-27.0.2.EL.src.rpm
updates/i386/RPMS/kernel-BOOT-2.4.21-27.0.2.EL.i386.rpm
updates/i386/RPMS/kernel-doc-2.4.21-27.0.2.EL.i386.rpm
updates/i386/RPMS/kernel-hugemem-2.4.21-27.0.2.EL.i686.rpm
updates/i386/RPMS/kernel-hugemem-unsupported-2.4.21-27.0.2.EL.i686.rpm
updates/i386/RPMS/kernel-smp-2.4.21-27.0.2.EL.athlon.rpm
updates/i386/RPMS/kernel-smp-2.4.21-27.0.2.EL.i686.rpm
updates/i386/RPMS/kernel-smp-unsupported-2.4.21-27.0.2.EL.athlon.rpm
updates/i386/RPMS/kernel-smp-unsupported-2.4.21-27.0.2.EL.i686.rpm
updates/i386/RPMS/kernel-source-2.4.21-27.0.2.EL.i386.rpm
updates/i386/RPMS/kernel-unsupported-2.4.21-27.0.2.EL.athlon.rpm
updates/i386/RPMS/kernel-unsupported-2.4.21-27.0.2.EL.i586.rpm
updates/i386/RPMS/kernel-unsupported-2.4.21-27.0.2.EL.i686.rpm

updates/i386/SRPMS/kernel-2.4.21-27.0.2.EL.src.rpm

These files are on mirror.caosity.org now and should be on all local mirrors within a few hours.

To update run yum update kernel

You will need to reboot to use the new kernel after update.