(RHSA-2003:223) stunnel security update

Stunnel is a wrapper for network connections. It can be used to tunnel an
unencrypted network connection over a secure connection (encrypted using
SSL or TLS) or to provide a secure means of connecting to services that do
not natively support encryption.

When configured to listen for incoming connections (instead of being
invoked by xinetd), stunnel can be configured to either start a thread or a
child process to handle each new connection. If Stunnel is configured to
start a new child process to handle each connection, it will receive a
SIGCHLD signal when that child exits.

Stunnel versions prior to 4.04 would perform tasks in the SIGCHLD signal
handler which, if interrupted by another SIGCHLD signal, could be unsafe.
This could lead to a denial of service.

All users are urged to upgrade to these errata packages, which modify
stunnel’s signal handler so that it is not vulnerable to this issue.

NOTE: After upgrading, any instances of stunnel configured to run in daemon
mode should be restarted, and any active network connections that are
currently being serviced by stunnel should be terminated and reestablished.