CentOS Errata and Security Advisory 2005:543
https://rhn.redhat.com/errata/RHSA-2005-543.html
The following updated files have been uploaded and are currently syncing to the mirrors:
i386: irb-1.8.1-7.EL4.1.i386.rpm ruby-1.8.1-7.EL4.1.i386.rpm ruby-devel-1.8.1-7.EL4.1.i386.rpm ruby-docs-1.8.1-7.EL4.1.i386.rpm ruby-libs-1.8.1-7.EL4.1.i386.rpm ruby-mode-1.8.1-7.EL4.1.i386.rpm ruby-tcltk-1.8.1-7.EL4.1.i386.rpm
src: ruby-1.8.1-7.EL4.1.src.rpm