poppassd offers the ability to change user's unix password over the network.
It serves as backend for several password changers like the SquirrelMail
plugin "Change Password" (http://squirrelmail.org/plugin_view.php?id=21).

Features:
** Poppassd strictly isolates the WWW interface from actual password
|  manipulations

** The program contains no known security bugs that could be reported
|  since it was released several years ago

** This version uses PAM, which means you can do anything PAM can.
|  Currently there are PAM modules for almost all known authentication
|  methods available

Internal poppassd version:
** 1.8.5 from http://ipsec.pl/pubs/poppassd.php