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Home » Hacking News » SuSE SA:2003:035: Sendmail remote denial of service

SuSE SA:2003:035: Sendmail remote denial of service

by Nikola Strahija on August 26th, 2003 Some versions of sendmail (8.12.0 through 8.12.8) contain a programming error in the code that implements DNS maps. A malformed DNS reply packet may cause sendmail to call `free()' on an uninitialized pointer.

SuSE Security Announcement

Package: sendmail
Announcement-ID: SuSE-SA:2003:035
Date: Tuesday, Aug 26th 2003 19:00 MEST
Affected products: 8.0, 8.1, 8.2
SuSE Linux Enterprise Server 8
remote denial-of-service
Severity (1-10): 5
SuSE default package: no
Cross References: CAN-2003-0688

Content of this advisory:
1) security vulnerability resolved: calling free() with arbitrary
problem description, discussion, solution and upgrade information
2) pending vulnerabilities, solutions, workarounds:
- traceroute(-nanog)
- gdm2
- pam_smb
- exim
3) standard appendix (further information)


1) problem description, brief discussion, solution, upgrade information

The well known and widely used MTA sendmail is vulnerable to a
remote denial-of-service attack in version 8.12.8 and earlier (but not
before 8.12). The bug exists in the DNS map code. This feature is
enabled by specifying FEATURE(`enhdnsbl').
When sendmail receives an invalid DNS response it tries to call free(3)
on random data which results in a process crash.

After your system was updated you have to restart your sendmail daemon
to make the update effective.

There is no known workaround for this vulnerability other than using a
different MTA.

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.

Intel i386 Platform:
patch rpm(s):
source rpm(s):

patch rpm(s):
source rpm(s):

patch rpm(s):
source rpm(s):

Intel i386 Platform:

patch rpm(s):
source rpm(s):

patch rpm(s):
source rpm(s):
patch rpm(s):
source rpm(s):


2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- traceroute(-nanog)
A integer overflow in traceroute can be abused by local attackers
to gain access to a raw IP socket.
New packages are available on out FTP servers.

- gdm2
Due to a bug in GDM it is possible for local users to read any text
file on a system by creating a symlink from ~/.xsession-errors.
Updated packages will be available on our FTP servers soon.

- pam_smb
A buffer overflow in the password handling function of pam_smb
allows remote root compromise.
Fixed packages will be available soon.

- exim
Two bugs where fixed in exim. One bug allows remote access as user
mail/mail and the other one allows local root access for 'Admin Users'.
Fixed packages are available on our FTP servers.


3) standard appendix: authenticity verification, additional information

- 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:
1) md5sums as provided in the (cryptographically signed) announcement.
2) using the internal gpg signatures of the rpm package.

1) execute the command
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 protected]),
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.

2) rpm package signatures provide an easy way to verify the authenticity
of an rpm package. Use the command
rpm -v --checksig
to verify the signature of the package, where 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.
a) gpg is installed
b) 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 "[email protected]" 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 .

- SuSE runs two security mailing lists to which any interested party may

[email protected]
- general/linux/SuSE security discussion.
All SuSE security announcements are sent to this list.
To subscribe, send an email to

[email protected]
- SuSE's announce-only mailing list.
Only SuSE's security announcements are sent to this list.
To subscribe, send an email to

For general information or the frequently asked questions (faq)
send mail to:

SuSE's security contact is or .
The public key is listed below.

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.

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