Advisory ID: cisco-sa-20090304-sbc
For Public Release 2009 March 4 16:00 UTC (GMT)
A denial of service (DoS) vulnerability exists in the Cisco Session
Border Controller (SBC) for the Cisco 7600 series routers. Cisco has released
free software updates that address this vulnerability. Workarounds that
mitigate this vulnerability are available.
This advisory is posted at
All Cisco ACE-based SBC modules running software versions prior to
3.0(2) are affected.
To determine the version of the Cisco SBC software running on a system,
log in to the device and issue the show version command to
display the system banner.
card_A/Admin# show version
system image file: [LCP] disk0:c76-sbck9-mzg.3.0.1_AS3_0_00.bin
Cisco SBC software version 3.0.1 is running in the device used in this
The Cisco XR 12000 Series SBC is not vulnerable. Additionally, the
Cisco ACE Module, Cisco ACE 4710 Application Control Engine, Cisco ACE XML
Gateway, Cisco ACE Web Application Firewall, and the Cisco ACE GSS (Global Site
Selector) 4400 Series are not affected by this vulnerability. No other Cisco
products are currently known to be affected by this vulnerability.
The Session Border Controller (SBC) enables direct IP-to-IP
interconnect between multiple administrative domains for session-based services
providing protocol interworking, security, and admission control and
management. The SBC is a multimedia device that sits on the border of a network
and controls call admission to that network. A vulnerability exists in the
Cisco SBC where an unauthenticated attacker may cause the Cisco SBC card to
reload by sending crafted TCP packets over port 2000. Repeated exploitation
could result in a sustained DoS condition.
Note: Only the Cisco SBC module reloads after successful exploitation. The
Cisco 7600 series router does not reload and it is not affected by this
Note: TCP port 2000 is typically used by Skinny Call Control Protocol
(SCCP) applications. However, the Cisco SBC module uses TCP port 2000 for high
availability (redundancy) communication, but does not use the SCCP for this
This vulnerability is documented in Cisco Bug IDs
registered customers only)
; and has been assigned
the Common Vulnerability and Exposures (CVE) IDs CVE-2009-0619.
Cisco has provided scores for the vulnerability in this advisory based
on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this
Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys
vulnerability severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can
then compute environmental scores to assist in determining the impact of the
vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions
regarding CVSS at
Cisco has also provided a CVSS calculator to help compute
the environmental impact for individual networks at
CSCsq18958 - Crafted TCP packet may crash SBC
Calculate the environmental score of
CVSS Base Score - 7.8
CVSS Temporal Score - 6.4
Successful exploitation of the vulnerability may cause a reload of the
affected device. Repeated exploitation could result in a sustained DoS
This vulnerability has been corrected in Cisco SBC software release
Cisco SBC software can be downloaded from:
When considering software upgrades, also consult
and any subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should exercise caution to be
certain the devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported properly by
the new release. If the information is not clear, contact the Cisco Technical
Assistance Center (TAC) or your contracted maintenance provider for assistance.
As a workaround, configure an access control list (ACL) in the
signaling / media VLAN on the Route Processor (RP). The following examples show
how VLAN 140 is configured as the signaling / media VLAN. A separate VLAN (VLAN
77) is configured as Fault Tolerance (FT). An ACL is added to the
signaling/media VLAN on the RP filtering all TCP port 2000 packets to the alias
Cisco SBC configuration
interface vlan 140
ip address 10.140.1.90 255.255.255.0
alias 10.140.1.100 255.255.255.0
peer ip address 10.140.1.8 255.255.255.0
ft interface vlan 77
ip address 192.168.1.1 255.255.255.0
peer ip address 192.168.1.8 255.255.255.0
!- ACL blocking all TCP port 2000 traffic to the 10.140.1.0 internal network
access-list 100 deny tcp any host 10.140.1.100 eq 2000
access-list 100 permit ip any any
ip address 10.140.1.1 255.255.255.0
!- ACL is applied to the VLAN interface to egress traffic
ip access-group 100 out
The alias command under VLAN 140 is configured with an IP address that
floats between active and standby modules when using high availability. Only
TCP port 2000 traffic destined to this IP address may trigger this
vulnerability. An access control list (ACL) is configured to deny TCP port 2000
destined to the alias IP address (10.140.1.100). The ACL is applied egress in
Note: TCP port 2000 is used by Skinny Call Control Protocol (SCCP)
applications; however, in this case it is used by the SBC for internal
communications. The previous ACL only blocks TCP port 2000 traffic to the alias
IP address. TCP port 2000 is not used by the alias IP address. This ACL should
not cause any collateral damage.
Additional mitigations that can be deployed on Cisco devices within the
network are available in the Cisco Applied Intelligence companion document for
Cisco has released free software updates that address this
vulnerability. Prior to deploying software, customers should consult their
maintenance provider or check the software for feature set compatibility and
known issues specific to their environment.
Customers may only install and expect support for the
feature sets they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound by the
terms of Cisco's software license terms found at
or as otherwise set forth at Cisco.com Downloads at
Do not contact firstname.lastname@example.org or email@example.com
for software upgrades.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
Customers whose Cisco products are provided or maintained through prior
or existing agreements with third-party support organizations, such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for guidance and assistance with the appropriate course of
action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on
specific customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected products
and releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.
Customers who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale should
acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC
contacts are as follows.
+1 800 553 2447 (toll free from within North America)
+1 408 526 7209 (toll call from anywhere in the world)
Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to a free
upgrade. Free upgrades for non-contract customers must be requested through the
for additional TAC contact information, including localized telephone numbers,
and instructions and e-mail addresses for use in various languages.
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
This vulnerability was found during internal testing.
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A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.
This advisory is posted on Cisco's worldwide website at :
In addition to worldwide web posting, a text version of
this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing lists or
newsgroups. Users concerned about this problem are encouraged to check the
above URL for any updates.
Initial public release