Which XSLT Processor does CF8 use?

I'm writing some XSLTs and would like to use the fn:base-uri() that is accessible in Saxon-SA 9.1.0.7 or later editions.  I cannot find any documentation on which XSLT processor(s) CF8 uses.  Nor can I find anything on possibly upgrading it or using CF to access an external processor.  Can anyone point me in the right direction on how to do upgrade CF8's XSLT processor, use another one via CF or even another function that the fn:base-uri() can do.

What I'm trying to do with the function is to get the XML's file name so that I can parse it out and insert it into the transformed XML.

EXAMPLE XSLT:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="2.0">

    <xsl:output method="xml"/>

    <xsl:variable name="filepath">
        <xsl:value-of select="base-uri()"/>
    </xsl:variable>

     <xsl:template match="/">

          <xsl:value-of select="$filepath"/>

     </xsl:template>

</xsl:stylesheet>