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Cisco Security Advisory: Denial of Service Vulnerability in
Cisco Wide
Area Application Services (WAAS) Software
Advisory ID: cisco-sa-20070718-waas
http://www.cisco.com/warp/public/707/cisco-sa-2
0070718-waas.shtml
Revision 1.0
For Public Release 2007 July 18 1600 UTC (GMT)
+-----------------------------------------------------------
-----------
Summary
=======
The Cisco Wide Area Application Services (WAAS) software
contains a
denial of service (DoS) vulnerability that may cause some
devices
that run WAAS software (WAE appliance and NM-WAE-502 module)
to stop
processing all types of traffic, including data traffic and
management
traffic. This condition may occur if a device running WAAS
software is
configured for Edge Services, which utilizes Common Internet
File System
(CIFS) optimization and receives a flood of TCP SYN packets
on port 139
or 445.
Cisco has made free software available to address this
vulnerability for
affected customers. Workarounds are available to mitigate
the effects of
this vulnerability.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-
20070718-waas.shtml.
Affected Products
=================
Vulnerable Products
+------------------
The vulnerability described in this document applies to both
the
WAE appliance and the NM-WAE-502 network module with Edge
Services
configured, which use CIFS optimization. Edge Services and
CIFS
optimization are disabled by default. CIFS functionality is
only
available once Edge Services are manually configured from
the WAAS
Central Manager. Only WAAS software versions 4.0.7 and 4.0.9
are
affected by this vulnerability.
In order to determine whether Edge Services are configured
and to
display the WAAS software version information, use the WAAS
Central
Manager GUI. The "show version" EXEC command from
the CLI will also
display the WAAS software version information.
Determine whether Edge Services are configured and display
the WAAS
software version information by following the steps below.
1. Log on to WAAS Central Manager.
2. Select the "Devices" tab.
3. Look under the Services column. "Edge" will
denote if Edge
Services are configured.
4. Look under the Software Version column. The software
version for
each device is identified.
The example below shows the output of the "show
version" command from a
WAE appliance CLI. In this example, the WAE is running
version 4.0.9.
CE-115-16#show version
Cisco Wide Area Application Services Software (WAAS)
Copyright (c) 1999-2007 by Cisco Systems, Inc.
Cisco Wide Area Application Services Software Release
4.0.9 (build b10 Apr 6 2007)
Version: fe611-4.0.9.10
Compiled 15:26:06 Apr 6 2007 by cnbuild
System was restarted on Sat Jun 16 05:03:41 2007.
The system has been up for 33 minutes, 40 seconds.
CE-115-16#
Products Confirmed Not Vulnerable
+--------------------------------
No other Cisco products or versions of WAAS software that
are not
explicitly identified in this advisory are currently known
to be
affected by this vulnerability.
WAE appliances and NM-WAE-502 modules that are not
configured to
provide Edge Services performing CIFS optimization are not
affected.
The NM-WAE-302 is not susceptible to this vulnerability as
it cannot be
configured for CIFS optimization.
Details
=======
The Cisco Wide Area Application Services solution uses a
combination of
application acceleration and WAN optimization techniques to
mitigate
application and transport latency. WAAS software is utilized
on the Wide
Area Application Engine appliance and the Wide Area
Application Services
Network Module that are incorporated in the solution.
A DoS vulnerability exists in some versions of WAAS software
that may
cause some devices that run WAAS software (WAE appliance
and
NM-WAE-502 module) to stop processing all types of traffic,
including
traffic going through the device (data traffic) and traffic
terminating on the device (management traffic). If the WAAS
device
has Edge Services, which uses CIFS optimization configured,
and
receives a flood of TCP SYN packets on ports 139 or 445,
this
vulnerability may be triggered, resulting in a DoS
condition. Ports
139 and 445 are utilized by the CIFS functionality of the
WAAS
software. This condition may result from network traffic
that is sent
directly to the WAAS platform, or by automated systems such
as
hostscanners, portscanners, or network worms.
This vulnerability is documented in Cisco Bug ID
CSCsi58809.
Vulnerability Scoring Details
+----------------------------
Cisco is providing 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 1.0.
Cisco will provide a base and temporal score. Customers can
then
compute environmental scores to assist in determining the
impact of the
vulnerability in individual networks.
Cisco PSIRT will set the bias in all cases to normal.
Customers
are encouraged to apply the bias parameter when determining
the
environmental impact of a particular vulnerability.
CVSS is a standards-based scoring method that conveys
vulnerability
severity and helps determine urgency and priority of
response.
Cisco has provided an FAQ to answer additional questions
regarding
CVSS at
http://www.cisco.com/web/about/security/in
telligence/cvss-qandas.html.
Cisco has also provided a CVSS calculator to help compute
the
environmental impact for individual networks at
http://intellishield.cisco.com/security/alertmanager/c
vss.
CSCsi58809: SYN flood causes device to become unresponsive
CVSS Base Score: 3.3
Access Vector: Remote
Access Complexity: Low
Authentication: Not Required
Confidentiality Impact: None
Integrity Impact: None
Availability Impact: Complete
Impact Bias: Normal
CVSS Temporal Score: 2.7
Exploitability: Functional
Remediation Level: Official Fix
Report Confidence: Confirmed
Impact
======
Successful exploitation of the vulnerability described in
this document
may allow a remote host to cause a device that is running an
affected
version of the WAAS software with Edge Services using CIFS
optimization
configured to enter into an unresponsive state. During this
unresponsive
state, no services are provided, including management access
to the
device. Recovery of the system from this unresponsive state
can only
be accomplished by resetting or power cycling the affected
device. The
following process can be used to remotely recover the
NM-WAE-502.
Remote Recovery of the NM-WAE-502
+--------------------------------
Log in to the router and issue the following command from
IOS CLI to
reboot the NM-WAE-502:
Router# service-module integrated-Service-Engine
<slot>/<port> reset
Software Version and Fixes
==========================
When considering software upgrades, also consult
http://www.cisco.com/go
/psirt and any subsequent advisories to determine
exposure and a complete upgrade solution.
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.
This vulnerability is fixed in version 4.0.11 of the Cisco
WAAS
software. WAAS public software releases have version numbers
that end in
odd numbers and can be downloaded from the following URL:
http://www.cisco.com/pcgi-bin/tablebuild.pl/waas4
0?psrtdcat20e2
Workarounds
===========
If the device that is running WAAS software does not need to
provide
Edge Services, then disabling Edge Services is a viable
workaround. When
the Edge Services are turned off, CIFS clients may not
benefit from the
response time reduction that is associated with the
operation of the
CIFS cache, preposition and other CIFS latency
optimizations. However,
other Layer 4 optimizations will continue to apply according
to the
application policy settings.
In order to disable Edge Services, which includes the CIFS
accelerator
and CIFS auto discovery features, follow the steps below.
1. Log in to WAAS Central Manager.
2. Select the "Devices" tab.
3. Select the "Devices" category (or "Device
Groups" if using
multiple devices in groups).
4. Choose target device or group.
5. Choose "File Services" located in the left
column under
"Contents."
6. Choose "Edge configuration" located under
"File Services."
7. Uncheck "Enable Edge Server."
8. Click Submit.
Transit ACLs (tACL)
+------------------
Filters that block access to TCP ports 139 and 445 packets
should be
deployed at the network edge as part of a transit access
list, which
will protect the router where the filter is configured as
well as
other devices behind it. Filters should also be deployed in
front of
vulnerable network devices so that TCP ports 139 and 445
packets are
only allowed from trusted CIFS Clients to trusted CIFS
Servers.
Further information about transit ACLs is available in the
white
paper "Transit Access Control Lists: Filtering at Your
Edge" at
the following link:
http://www.cisco.com/e
n/US/tech/tk648/tk361/technologies_white_paper09186a00801afc
76.shtml
Further information about configuring ACLs on the WAAS
client
is in the "Creating and Managing IP Access Control
Lists for
WAAS Devices" chapter of the WAAS Configuration Guide
at the
following link:
http://www.c
isco.com/en/US/products/ps6870/products_configuration_guide_
chapter09186a00807bb6b9.html
Additional mitigations that can be deployed on Cisco devices
within
the network are discussed in the Cisco Applied Intelligence
companion
document for this advisory available at the following link:
http://www.cisco.com/warp/public/707/cisco-air
-20070718-waas.shtml
Obtaining Fixed Software
========================
Cisco will make free software available to address this
vulnerability
for affected customers. This advisory will be updated as
fixed software
becomes available. 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 http://www.cisco.com/public/sw-license-agreement.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact either "psirt cisco.com" or
"security-alertcisco.com"
for software upgrades.
Customers with Service Contracts
+-------------------------------
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 http://www.cisco.com.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained
through prior
or existing agreement 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 without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but who do not hold
a Cisco
service contract and customers who purchase through
third-party vendors
but are unsuccessful at obtaining fixed software through
their point
of sale should obtain their 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)
* e-mail: taccisco.com
Have your product serial number available and give the URL
of this
notice as evidence of your entitlement to a free upgrade.
Free upgrades
for non-contract customers must be requested through the
TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC
.shtml
for additional TAC contact information, including special
localized
telephone numbers and instructions and e-mail addresses for
use in
various languages.
Exploitation and Public Announcements
=====================================
The Cisco PSIRT is not aware of any public announcements or
malicious
use of the vulnerability described in this advisory.
This vulnerability was discovered during the resolution of
customer
support cases.
Status of this Notice: FINAL
============================
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND
DOES NOT IMPLY
ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES
OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF
THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE
DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR
UPDATE THIS
DOCUMENT AT ANY TIME.
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.
Distribution
============
This advisory is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-2
0070718-waas.shtml
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.
* cust-security-announcecisco.com
* first-teamsfirst.org
* bugtraqsecurityfocus.com
* vulnwatchvulnwatch.org
* ciscospot.colorado.edu
* cisco-nsppuck.nether.net
* full-disclosurelists.grok.org.uk
* comp.dcom.sys.cisconewsgate.cisco.com
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.
Revision History
================
+-----------------------------------------------------------
+
| Revision 1.0 | 2007-July-18 | Initial public release
|
+-----------------------------------------------------------
+
Cisco Security Procedures
=========================
Complete information on reporting security vulnerabilities
in
Cisco products, obtaining assistance with security
incidents, and
registering to receive security information from Cisco, is
available
on Cisco's worldwide website at
http://www.cisco.com/en/US/produ
cts/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding
Cisco security
notices. All Cisco security advisories are available at
http://www.cisco.com/g
o/psirt.
+-----------------------------------------------------------
---------
All contents are Copyright(C) 2006-2007 Cisco Systems, Inc.
All rights reserved.
+-----------------------------------------------------------
---------
Updated: Jul 18, 2007 Document
ID: 92020
+-----------------------------------------------------------
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