Moderate: dnsmasq (SL6)

Synopsis: Moderate: dnsmasq security, bug fix and enhancement update
Issue Date: 2013-02-21
CVE Numbers: CVE-2012-3411

It was discovered that dnsmasq, when used in combination with certain libvirtd
configurations, could incorrectly process network packets from network
interfaces that were intended to be prohibited. A remote, unauthenticated
attacker could exploit this flaw to cause a denial of service via DNS
amplification attacks. (CVE-2012-3411)

In order to fully address this issue, libvirt package users are advised to
install updated libvirt packages.

This update also fixes the following bug:

* Due to a regression, the lease change script was disabled. Consequently, the
“dhcp-script” option in the /etc/dnsmasq.conf configuration file did not work.
This update corrects the problem and the “dhcp-script” option now works as

This update also adds the following enhancements:

* Prior to this update, dnsmasq did not validate that the tftp directory given
actually existed and was a directory. Consequently, configuration errors were
not immediately reported on startup. This update improves the code to validate
the tftp root directory option. As a result, fault finding is simplified
especially when dnsmasq is called by external processes such as libvirt.

* The dnsmasq init script used an incorrect Process Identifier (PID) in the
“stop”, “restart”, and “condrestart” commands. Consequently, if there were some
dnsmasq instances running besides the system one started by the init script,
then repeated calling of “service dnsmasq” with “stop” or “restart” would kill
all running dnsmasq instances, including ones not started with the init script.
The dnsmasq init script code has been corrected to obtain the correct PID when
calling the “stop”, “restart”, and “condrestart” commands. As a result, if
there are dnsmasq instances running in addition to the system one started by
the init script, then by calling “service dnsmasq” with “stop” or “restart”
only the system one is stopped or restarted.

* When two or more dnsmasq processes were running with DHCP enabled on one
interface, DHCP RELEASE packets were sometimes lost. Consequently, when two or
more dnsmasq processes were running with DHCP enabled on one interface,
releasing IP addresses sometimes failed. This update sets the SO_BINDTODEVICE
socket option on DHCP sockets if running dnsmasq with DHCP enabled on one
interface. As a result, when two or more dnsmasq processes are running with
DHCP enabled on one interface, they can release IP addresses as expected.


– Scientific Linux Development Team