What is the exposure to the recent libxml flaws revealed by Codenomicon?

I am uncertain whether libexpat shares the code with libxml et al.
Is this something to worry about?  If so, is a fix being worked on?

Thanks.

http://www.codenomicon.com/labs/xml/
http://www.theregister.co.uk/2009/08/06/xml_flaws/