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RedHat: 'stunnel' Format string vulnerability Print E-mail
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Posted by Team   
RedHat Linux Updated stunnel packages are now available for Red Hat Linux 7.2. Theseupdates close a format-string vulnerability which is present in someearlier versions of stunnel.

                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          Updated stunnel packages available.
Advisory ID:       RHSA-2002:002-10
Issue date:        2002-01-01
Updated on:        2002-01-03
Product:           Red Hat Linux
Keywords:          stunnel format string vulnerability
Cross references:  
Obsoletes:         RHSA-2000:137

1. Topic:

Updated stunnel packages are now available for Red Hat Linux 7.2.  These
updates close a format-string vulnerability which is present in some
earlier versions of stunnel.

2. Relevant releases/architectures:

Red Hat Linux 7.2 - i386, ia64

3. Problem description:

Stunnel is an SSL wrapper for applications.  One feature of Stunnel is the
ability to negotiate SSL with protocols using the '-n' flag. There are
format string bugs present in the functions which implement smtp, pop, and
nntp client negotiations as supplied with Stunnel versions 3.15 up to 3.21c. 

If you use Stunnel with the '-n smtp', '-n pop', '-n nntp' options with
the client mode '-c' option, a malicous server could abuse the format
string bug to run arbitrary code as the owner of the Stunnel process.  The
packages included update Stunnel to version 3.22 which is not vulnerable to
this bug.

The Common Vulnerabilities and Exposures project ( has
assigned the name CAN-2002-0002 to this issue.

4. Solution:

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

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.Red for more info):

6. RPMs required:

Red Hat Linux 7.2:




7. Verification:

MD5 sum                          Package Name
b0a3367f7369841f615b57e9de234703 7.2/en/os/SRPMS/stunnel-3.22-1.src.rpm
b62a3f6c4418550873602147697213b0 7.2/en/os/i386/stunnel-3.22-1.i386.rpm
6cc2a3665a608922159d583d1401ad20 7.2/en/os/ia64/stunnel-3.22-1.ia64.rpm

These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at:

You can verify each package with the following command:
    rpm --checksig  

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

8. References:

Copyright(c) 2000, 2001, 2002 Red Hat, Inc.

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