RHSA-2011:0262 - Security Advisory

Topic

Updated sendmail packages that fix one security issue and three bugs are
now available for Red Hat Enterprise Linux 4.

The Red Hat Security Response Team has rated this update as having low
security impact. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available from the CVE link in
the References section.

Description

Sendmail is a Mail Transport Agent (MTA) used to send mail between
machines.

A flaw was found in the way sendmail handled NUL characters in the
CommonName field of X.509 certificates. An attacker able to get a
carefully-crafted certificate signed by a trusted Certificate Authority
could trick sendmail into accepting it by mistake, allowing the attacker to
perform a man-in-the-middle attack or bypass intended client certificate
authentication. (CVE-2009-4565)

The CVE-2009-4565 issue only affected configurations using TLS with
certificate verification and CommonName checking enabled, which is not a
typical configuration.

This update also fixes the following bugs:

• Previously, sendmail did not correctly handle mail messages that had a

long first header line. A line with more than 2048 characters was split,
causing the part of the line exceeding the limit, as well as all of the
following mail headers, to be incorrectly handled as the message body.
(BZ#499450)

• When an SMTP-sender is sending mail data to sendmail, it may spool that

data to a file in the mail queue. It was found that, if the SMTP-sender
stopped sending data and a timeout occurred, the file may have been left
stalled in the mail queue, instead of being deleted. This update may not
correct this issue for every situation and configuration. Refer to the
Solution section for further information. (BZ#434645)

• Previously, the sendmail macro MAXHOSTNAMELEN used 64 characters as the

limit for the hostname length. However, in some cases, it was used against
an FQDN length, which has a maximum length of 255 characters. With this
update, the MAXHOSTNAMELEN limit has been changed to 255. (BZ#485380)

All sendmail users should upgrade to these updated packages, which contain
backported patches to correct these issues. After installing this update,
sendmail will be restarted automatically.

Solution

As part of the fix for BZ#434645, a script called purge-mqueue is shipped
with this update. It is located in the /usr/share/sendmail/ directory. The
primary purpose of this script is a one-time clean up of the mqueue from
stalled files that were created before the installation of this update. By
default, the script removes all files from /var/spool/mqueue/ that have an
atime older than one month. It requires the tmpwatch package to be
installed. If you have stalled files in your mqueue you can run this script
or clean them manually. It is also possible to use this script as a cron
job (for example, by copying it to /etc/cron.daily/), but it should not be
needed in most cases, because this update should prevent the creation of
new stalled files.

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

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux Server 4 x86_64
• Red Hat Enterprise Linux Server 4 ia64
• Red Hat Enterprise Linux Server 4 i386
• Red Hat Enterprise Linux Workstation 4 x86_64
• Red Hat Enterprise Linux Workstation 4 ia64
• Red Hat Enterprise Linux Workstation 4 i386
• Red Hat Enterprise Linux Desktop 4 x86_64
• Red Hat Enterprise Linux Desktop 4 i386
• Red Hat Enterprise Linux for IBM z Systems 4 s390x
• Red Hat Enterprise Linux for IBM z Systems 4 s390
• Red Hat Enterprise Linux for Power, big endian 4 ppc

Fixes

• BZ - 434645 - DATA timeouts leave behind stale df files in mqueue
• BZ - 485380 - sendmail applies MAXHOSTNAMELEN for FQDN.
• BZ - 552622 - CVE-2009-4565 sendmail: incorrect verification of SSL certificate with NUL in name

CVEs

• CVE-2009-4565

References

• https://access.redhat.com/security/updates/classification/#low