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Date: Fri, 06 Sep 2013 23:53:40 +0200
From: Jakub Jozwiak <>
Subject: Check Point ClusterXL/CCP issue (DoS)

Hi List,

Recently I found issue with ClusterXL/CCP operation on Check Point
gateways - you can find details below:

Issue description

Issue occurs when specially crafted CCP packets are send to all Check
Point ClusterXL cluster members. This causes clustered gateway to be
confused about state of its peer(s) which can lead to situation when all
cluster members end up in Ready/Standby state. Such case leads to denial
of service where none cluster member will forward network traffic.

For attack to be successful attacker must be able to sniff CCP traffic
which requires him/her to have direct access to broadcast domain in
which "Sync" or "Cluster + Sync" interfaces are located. In many cases
this requirement may considerably limit attack surface.

Issue concerns following ClusterXL modes:

* New High Availability
* Load Sharing (Unicast)
* Load Sharing (Multicast)

Product information

Issue affects operation of ClusterXL clusters utilizing CCP as
underlying protocol.

"ClusterXL Administration Guide R75" defines ClusterXL and CCP in the
following way:

(page 8)
"A ClusterXL cluster is a group of identical Check Point Security
Gateways connected in such a way that if one fails, another immediately
takes its place.  ClusterXL is a software-based Load Sharing and High
Availability solution that distributes network traffic between clusters
of redundant Security Gateways and provides transparent failover between
machines in a cluster."

(page 9)
"The Cluster Control Protocol (CCP) is the glue that links together the
machines in the Check Point Gateway Cluster. CCP traffic is distinct
from ordinary network traffic and can be viewed using any network sniffer."

Technical details

High level description of the attack can be summarized in the following

  1. Sniff for all CCP packets generated by cluster members
  2. From all sniffed packets select only "CCP Report source machine's
     state" packets (opcode = 1)
  3. For each selected packet set all payload bytes to 0
  4. Send back packet to wire leaving all other fields untouched

Ad 1. CCP runs over UDP and utilizes port 8116 for both source and
destination. Note that in most configurations CCP packets are send also
on interfaces which are not defined as "Sync".

Ad 4. Especially following fields should match those from original frame:
  * CCP header fields
  * Source MAC should match following pattern:
    00:00:00:00:magic_number:member_id, where magic_number in default
    configuration equals to 0xfe, member_id can be random
  * Destination MAC in multicast mode should match 01:00:05:xx:yy:zz
    where xx:yy:zz reflects last 3 octets of cluster virtual IP

Attached PoC consists of two files:

  * `ccp-kill.rb` - actual PoC code. It takes only one argument -
    interface name on which it will sniff and send CCP packets. It has
    been tested on BackTrack 5R3 with Ruby 1.8 and requires following
    Ruby gems: Racket, Pcaprub.
  * `ccp.rb` - extension file for Racket describing CCP protocol fields
    (based on Wireshark CCP dissector). It needs to be placed in
    `lib/racket/l5` dir where Racket gem is installed

Running PoC on network where cluster "Sync" or "Cluster + Sync"
interfaces are located will cause cluster members transitioning from
Active/Standby or Active/Active states to Ready/Ready (Load Sharing) or
Ready/Standby (New High Availability). In this scenario none of cluster
members will handle network traffic which is utilizing cluster virtual
IP address as a gateway.

Affected versions

So far tests have been performed on SPLAT-based R75 Check Point gateway
installation reporting following version: R75 - Build 254 and CCP
packets reporting following version: 2000.

My (uneducated) guess is that at least other versions from R75 line
would behave in presented manner.

Vendor response

Vendor has been informed about the issue and came back with following

"Check Point Cluster Control protocol is assumed to be sent over a
trusted network. Customer may achieve this by using a dedicated physical
network segment or by using VLANs. It is the responsibility of the
customer to ensure that the network is trusted."

Additionally vendor confirmed that in future releases packet digital
signatures for CCP will be introduced.


Vendor response as well as already mentioned "ClusterXL Administration
Guide R75" (page 11) give hints about proper network design that will
minimize possibility of the attack. Especially running "Cluster + Sync"
interfaces which usually mix both sync and 'normal' network traffic
should be avoided.


Download attachment "ccp.rb" of type "application/x-ruby" (719 bytes)

Download attachment "ccp-kill.rb" of type "application/x-ruby" (2884 bytes)

Download attachment "signature.asc" of type "application/pgp-signature" (837 bytes)

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