Libxml2 is a library for manipulating XML files. A flaw in the way libxml2 parses remote data retrieved using FTP or HTTP could be exploited to cause a buffer overflow. This in turn could be used to run arbitrary code on the affected machine.
Users of Red Hat 9 are advised to upgrade.
For details, see https://rhn.redhat.com/errata/RHSA-2004-091.html.