Updated bind packages that help mitigate DNS spoofing attacks are now
This update has been rated as having important security impact by the Red
Hat Security Response Team.
[Updated 10th July 2008]
We have updated the Enterprise Linux 5 packages in this advisory. The
default and sample caching-nameserver configuration files have been updated
so that they do not specify a fixed query-source port. Administrators
wishing to take advantage of randomized UDP source ports should check their
configuration file to ensure they have not specified fixed query-source ports.
ISC BIND (Berkeley Internet Name Domain) is an implementation of the DNS
(Domain Name System) protocols.
The DNS protocol protects against spoofing attacks by requiring an attacker
to predict both the DNS transaction ID and UDP source port of a request. In
recent years, a number of papers have found problems with DNS
implementations which make it easier for an attacker to perform DNS
Previous versions of BIND did not use randomized UDP source ports. If an
attacker was able to predict the random DNS transaction ID, this could make
DNS cache-poisoning attacks easier. In order to provide more resilience,
BIND has been updated to use a range of random UDP source ports.
Note: This errata also updates SELinux policy on Red Hat Enterprise Linux 4
and 5 to allow BIND to use random UDP source ports.
Users of BIND are advised to upgrade to these updated packages, which
contain a backported patch to add this functionality.
Red Hat would like to thank Dan Kaminsky for reporting this issue.