Stunnel 4.00, and 3.24 and earlier, leaks a privileged file descriptor returned by listen(), which allows local users to hijack the Stunnel server.
http://www.redhat.com/support/errata/RHSA-2003-297.html
http://www.mandriva.com/security/advisories?name=MDKSA-2003:108
http://marc.info/?l=bugtraq&m=106260760211958&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000736