Package : dhcp3 Vulnerability : ignored counter boundary Problem-Type : remote Debian-specific: no CVE Id : CAN-2003-0039
Florian Lohoff discovered a bug in the dhcrelay causing it to send a continuing packet storm towards the configured DHCP server(s) in case of a malicious BOOTP packet, such as sent from buggy Cisco switches.
When the dhcp-relay receives a BOOTP request it forwards the request to the DHCP server using the broadcast MAC address ff:ff:ff:ff:ff:ff which causes the network interface to reflect the packet back into the socket. To prevent loops the dhcrelay checks whether the relay-address is its own, in which case the packet would be dropped. In combination with a missing upper boundary for the hop counter an attacker can force the dhcp-relay to send a continuing packet storm towards the configured dhcp server(s).
This patch introduces a new commandline switch ``-c maxcount'' and people are advised to start the dhcp-relay with ``dhcrelay -c 10'' or a smaller number, which will only create that many packets.
The dhcrelay program from the ``dhcp'' package does not seem to be affected since DHCP packets are dropped if they were apparently relayed already.
For the stable distribution (woody) this problem has been fixed in version 3.0+3.0.1rc9-2.2.
The old stable distribution (potato) does not contain dhcp3 packages.
For the unstable distribution (sid) this problem has been fixed in version 1.1.2-1.
We recommend that you upgrade your dhcp3 package when you are using the dhcrelay server.
Upgrade Instructions --------------------
wget url will fetch the file for you dpkg -i file.deb will install the referenced file.
If you are using the apt-get package manager, use the line for sources.list as given below:
apt-get update will update the internal database apt-get upgrade will install corrected packages
You may use an automated update by adding the resources from the footer to the proper configuration.
Debian GNU/Linux 3.0 alias woody --------------------------------
