security vulnerability resolved: sendmail, sendmail-tls problem
description, discussion, solution and upgrade information
pending vulnerabilities, solutions, workarounds:
standard appendix (further information)
1) problem description, brief discussion, solution, upgrade
sendmail is the most widely used mail transport agent (MTA) in
the internet. A remotely exploitable buffer overflow has been found
in all versions of sendmail that come with SuSE products. These
versions include sendmail-8.11 and sendmail-8.12 releases. sendmail
is the MTA subsystem that is installed by default on all SuSE
products up to and including SuSE Linux 8.0 and the SuSE Linux
Enterprise Server 7.
The vulnerability discovered is known as the prescan()-bug and
is not related to the vulnerability found and fixed in April 2003.
The error in the code can cause heap or stack memory to be
overwritten, triggered by (but not limited to) functions that parse
There is no known workaround for this vulnerability other than
using a different MTA. The vulnerability is triggered by an email
message sent through the sendmail MTA subsystem. In that respect,
it is different from commonly known bugs that occur in the context
of an open TCP connection. By consequence, the vulnerability also
exists if email messages get forwarded over a relay that itself
does not run a vulnerable MTA. This specific detail and the wide
distribution of sendmail in the internet causes this vulnerability
to be considered a flaw of major severity. We recommend to install
the update packages that are provided for download at the locations
We thank Michal Zalewski who discovered this vulnerability and
the friendly people from Sendmail Inc (Claus Assmann) who have
communicated problem to SuSE Security.
Please download the update package for your distribution and
verify its integrity by the methods listed in section 3) of this
announcement. Then, install the package using the command "rpm -Fhv
file.rpm" to apply the update.
Our maintenance customers are being notified individually. The
packages are being offered to install from the maintenance web.
2) Pending vulnerabilities in SuSE Distributions and
As already announced in SuSE-SA:2003:038 and SuSE-SA:2003:039,
we are working on update packages for the mysql buffer overflow
vulnerability. The packages will be made available as soon as
3) standard appendix: authenticity verification, additional
Package authenticity verification:
SuSE update packages are available on many mirror ftp servers
all over the world. While this service is being considered valuable
and important to the free and open source software community, many
users wish to be sure about the origin of the package and its
content before installing the package. There are two verification
methods that can be used independently from each other to prove the
authenticity of a downloaded file or rpm package:
md5sums as provided in the (cryptographically signed)
using the internal gpg signatures of the rpm package.
execute the command md5sum <name-of-the-file.rpm> after
you downloaded the file from a SuSE ftp server or its mirrors.
Then, compare the resulting md5sum with the one that is listed in
the announcement. Since the announcement containing the checksums
is cryptographically signed (usually using the key email@example.com), the checksums show
proof of the authenticity of the package. We disrecommend to
subscribe to security lists which cause the email message
containing the announcement to be modified so that the signature
does not match after transport through the mailing list software.
Downsides: You must be able to verify the authenticity of the
announcement in the first place. If RPM packages are being rebuilt
and a new version of a package is published on the ftp server, all
md5 sums for the files are useless.
rpm package signatures provide an easy way to verify the
authenticity of an rpm package. Use the command rpm -v --checksig
<file.rpm> to verify the signature of the package, where
<file.rpm> is the filename of the rpm package that you have
downloaded. Of course, package authenticity verification can only
target an un-installed rpm package file. Prerequisites:
gpg is installed
The package is signed using a certain key. The public part of
this key must be installed by the gpg program in the directory
~/.gnupg/ under the user's home directory who performs the
signature verification (usually root). You can import the key that
is used by SuSE in rpm packages for SuSE Linux by saving this
announcement to a file ("announcement.txt") and running the command
(do "su -" to be root): gpg --batch; gpg < announcement.txt |
gpg --import SuSE Linux distributions version 7.1 and thereafter
install the key "firstname.lastname@example.org"
upon installation or upgrade, provided that the package gpg is
installed. The file containing the public key is placed at the
top-level directory of the first CD (pubring.gpg) and at ftp://ftp.suse.com/pub/suse/pubring.gpg-build.suse.de
SuSE runs two security mailing lists to which any interested
party may subscribe:
The information in this advisory may be distributed or
reproduced, provided that the advisory is not modified in any way.
In particular, it is desired that the clear-text signature shows
proof of the authenticity of the text.
SuSE Linux AG makes no warranties of any kind whatsoever with
respect to the information contained in this security advisory.