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Red Hat Linux Advisory: stunnel

Jul 25, 2003, 20:26 (0 Talkback[s])

Red Hat Security Advisory

Synopsis: Updated stunnel packages fix signal vulnerability
Advisory ID: RHSA-2003:221-01
Issue date: 2003-07-25
Updated on: 2003-07-25
Product: Red Hat Linux
Keywords: stunnel signal handler reentrancy DoS
Cross references:  
Obsoletes: RHSA-2002:002
CVE Names: CAN-2002-1563

1. Topic:

Updated stunnel packages are now available for Red Hat Linux 7.1, 7.2, 7.3, and 8.0. These updates correct a potential vulnerability in stunnel's signal handling.

2. Relevant releases/architectures:

Red Hat Linux 7.1 - i386
Red Hat Linux 7.2 - i386, ia64
Red Hat Linux 7.3 - i386
Red Hat Linux 8.0 - i386

3. Problem description:

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.

4. Solution:

Before applying this update, make sure all previously released errata relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade. Only those RPMs which are currently installed will be updated. Those RPMs which are not installed but included in the list will not be updated. Note that you can also use wildcards (*.rpm) if your current directory only contains the desired RPMs.

Please note that this update is also available via Red Hat Network. Many people find this an easier way to apply updates. To use Red Hat Network, launch the Red Hat Update Agent with the following command:


This will start an interactive process that will result in the appropriate RPMs being upgraded on your system.

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):

82325 - stunnel security errata required

6. RPMs required:

Red Hat Linux 7.1:



Red Hat Linux 7.2:




Red Hat Linux 7.3:



Red Hat Linux 8.0:



7. Verification:

MD5 sum Package Name

e20a6bcf06735897d4b9f7a05b9ded3f 7.1/en/os/SRPMS/stunnel-3.22-5.7.1.src.rpm
38a38be900e55173493db34a1d0fdddd 7.1/en/os/i386/stunnel-3.22-5.7.1.i386.rpm
d74e461c13ccb49a48bac85560b40287 7.2/en/os/SRPMS/stunnel-3.22-5.7.3.src.rpm
bc60108d725ce1b88bfdc16db0b9ee6f 7.2/en/os/i386/stunnel-3.22-5.7.3.i386.rpm
f017a9e4373a8478342961e430c8405f 7.2/en/os/ia64/stunnel-3.22-5.7.3.ia64.rpm
d74e461c13ccb49a48bac85560b40287 7.3/en/os/SRPMS/stunnel-3.22-5.7.3.src.rpm
bc60108d725ce1b88bfdc16db0b9ee6f 7.3/en/os/i386/stunnel-3.22-5.7.3.i386.rpm
37e3c19c87b1c47a3a503823ce19a687 8.0/en/os/SRPMS/stunnel-3.22-5.8.0.src.rpm
10a5bac0cf90d31b6db4b49abc74ca4b 8.0/en/os/i386/stunnel-3.22-5.8.0.i386.rpm

These packages are GPG signed by Red Hat for security. Our key is available from http://www.redhat.com/security/keys.html

You can verify each package with the following command:

rpm --checksig -v <filename>

If you only wish to verify that each package has not been corrupted or tampered with, examine only the md5sum with the following command:

md5sum <filename>

8. References:


9. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact details at http://www.redhat.com/solutions/security/news/contact.html

Copyright 2003 Red Hat, Inc.