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7.40. dnsmasq

Updated dnsmasq packages that fix one security issue, one bug, and add various enhancements are now available for Red Hat Enterprise Linux 6.
The Red Hat Security Response Team has rated this update as having moderate security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) associated with each description below.
The dnsmasq packages contain Dnsmasq, a lightweight DNS (Domain Name Server) forwarder and DHCP (Dynamic Host Configuration Protocol) server.

Security Fix

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.
In order to fully address this issue, libvirt package users are advised to install updated libvirt packages. Refer to RHSA-2013:0276 for additional information.

Bug Fix

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 expected.


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.
All users of dnsmasq are advised to upgrade to these updated packages, which fix these issues and add these enhancements.