Use the CFLDAP tag where ACTION="modify".
Basically, it would look something like this:
<cfldap action="modify" modifytype="replace"
attributes="sn=#lastname#;givenName=#firstName#" dn="#userDN#"
...[rest of attributes]...>
In the ATTRIBUTES attribute, you set any AD attributes that
need to be changed. These attribute/values are separated by a
semicolon. If any values should have a semicolon in them, then you
need to use the DELIMITER or SEPARATOR attributes to specify a
different character. I would suggest a tab character.