stunnel 4.0.3 and earlier allows attackers to cause a denial of service (crash) via SIGCHLD signal handler race conditions that cause an inconsistency in the child counter.
distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000736
marc.info/?l=bugtraq&m=104247606910598
marc.info/?l=bugtraq&m=106029168514511&w=2
marc.info/?l=stunnel-users&m=103600188215117&w=2
www.linuxsecurity.com/advisories/engarde_advisory-3535.html
www.redhat.com/support/errata/RHSA-2003-221.html
www.redhat.com/support/errata/RHSA-2003-223.html
www.securityfocus.com/bid/6592