CentOS Errata and Security Advisory 2005:584
https://rhn.redhat.com/errata/RHSA-2005-584.html
The following updated files have been uploaded and are currently syncing to the mirrors:
i386: zlib-1.2.1.2-1.2.i386.rpm zlib-devel-1.2.1.2-1.2.i386.rpm
src: zlib-1.2.1.2-1.2.src.rpm