[AusNOG] Cisco Security Advisory: Cisco ASR 9000 Series Routers Line Card IP Version 4 Denial of Service Vulnerability

Thu Jul 21 02:00:00 EST 2011

Cisco 9000 Series Aggregation Services Routers (ASR) running Cisco
IOS XR Software version 4.1.0 contain a vulnerability that may cause
a network processor in a line card to lock up while processing an IP
version 4 (IPv4) packet. As a consequence of the network processor
lockup, the line card that is processing the offending packet will
automatically reload.

Cisco has released a free software maintenance upgrade (SMU) to
address this vulnerability.

There are no workarounds for this vulnerability.

This advisory is posted at:
http://www.cisco.com/warp/public/707/cisco-sa-20110720-asr9k.shtml

Affected Products
=================

Vulnerable Products
+------------------

This vulnerability affects the following Cisco ASR 9000 Series
devices when they are running Cisco IOS XR Software version 4.1.0
without the SMU asr9k-p-4.1.0.CSCtr26695.tar installed:

  * Cisco ASR 9006 router
  * Cisco ASR 9010 router

To determine the software running on a Cisco ASR 9000 Series device,
log in to the device and issue the show version brief command to
display the system banner. The system banner confirms that the device
is running Cisco IOS XR Software by displaying text similar to Cisco
IOS XR Software. The software version is displayed after the text
Cisco IOS XR Software.

The following example identifies a Cisco ASR 9010 that is running
Cisco IOS XR Software Release 4.1.0:

    RP/0/0/CPU0:Router#show version brief
    Fri Jul  8 18:54:39.222 CEST

    Cisco IOS XR Software, Version 4.1.0[Default]
    Copyright (c) 2011 by Cisco Systems, Inc.

    ROM: System Bootstrap, Version 1.05(20101118:025914) [ASR9K ROMMON],

    Router uptime is 9 weeks, 1 day, 5 hours, 53 minutes
    System image file is "bootflash:disk0/asr9k-os-mbi-4.1.0/mbiasr9k-rp.vm"

    cisco ASR9K Series (MPC8641D) processor with 4194304K bytes of memory.
    MPC8641D processor at 1333MHz, Revision 2.2
    ASR-9010-CHASSIS

    4 Management Ethernet
    8 WANPHY controller(s)
    8 TenGigE
    8 DWDM controller(s)
    40 GigabitEthernet
    4 SONET/SDH
    2 Packet over SONET/SDH
    1 MgmtMultilink
    219k bytes of non-volatile configuration memory.
    975M bytes of compact flash card.
    33994M bytes of hard disk.
    1605616k bytes of disk0: (Sector size 512 bytes).
    1605616k bytes of disk1: (Sector size 512 bytes).

To determine which SMUs are active on the device, issue the show
install active summary command. This command will return a list of
all SMUs installed, as shown in the following example:

    RP/0/0/CPU0:Router#show install active summary
    Fri Jul  8 19:02:15.887 CEST
      Active Packages:
        disk0:asr9k-doc-p-4.1.0
        disk0:asr9k-mini-p-4.1.0
        disk0:asr9k-k9sec-p-4.1.0
        disk0:asr9k-video-p-4.1.0

Note: The preceding output shows a device without the SMU
asr9k-p-4.1.0.CSCtr26695.tar installed. Also note that Cisco IOS XR
Software can include multiple SMUs and the output may differ from the
preceding example.

Products Confirmed Not Vulnerable
+--------------------------------

The following products are confirmed not vulnerable:

  * Cisco Carrier Routing System (CRS) running any version of Cisco IOS XR Software
  * Cisco XR 12000 Series Routers running any version of Cisco IOS XR Software
  * Cisco 12000 Series Routers running any version of Cisco IOS Software
  * Cisco IOS Software
  * Cisco IOS XE Software
  * Cisco NX-OS Software
  * Cisco ASR 1000 and 5000 Series routers running any version of software
  * Cisco ASR 9000 Series routers running any version of Cisco IOS XR Software other than 4.1.0
  * Cisco ASR 9000 Series routers running Cisco IOS XR Software 
    version 4.1.0 and with the SMU asr9k-p-4.1.0.CSCtr26695.tar installed

    To determine which SMUs are active on the device, issue the show
    install active summary command. This will return a list of all
    SMUs installed:

        RP/0/0/CPU0:Router#show install active summary
        Fri Jul  8 19:02:15.887 CEST
          Active Packages:
            disk0:asr9k-p-4.1.0.CSCtr26695-1.0.0
            disk0:asr9k-p-4.1.0.CSCto96804-1.0.0
            disk0:asr9k-p-4.1.0.CSCto95435-1.0.0
            disk0:asr9k-doc-p-4.1.0
            disk0:asr9k-mini-p-4.1.0
            disk0:asr9k-k9sec-p-4.1.0
            disk0:asr9k-video-p-4.1.0

    Note: The preceding output shows a device with the SMU
    asr9k-p-4.1.0.CSCtr26695.tar installed (in bold). Also note that
    Cisco IOS XR Software can include multiple SMUs and the output
    may differ from the preceding example.

Details
=======

Cisco ASR 9000 Series routers are designed to provide carrier-class
reliability using the Cisco IOS XR Software modular operating system,
offering service and application-level intelligence focused on
optimized video delivery and mobile aggregation in Carrier Ethernet
Services networks.

Cisco IOS XR Software is a distributed operating system designed for
continuous system operation combined with service flexibility and
high performance.

Cisco ASR 9000 Series devices running Cisco IOS XR Software version
4.1.0 contain a vulnerability that may cause a network processor in a
line card to lock up while processing an IPv4 packet. As a
consequence of the network processor lockup, the line card that is
processing the offending packet will automatically reload.

This vulnerability can be triggered only by IPv4 packets. If only IP
version 6 (IPv6) is in use, the device is not vulnerable.

Both transit IPv4 packets and IPv4 packets directed to the device
itself may trigger this vulnerability.

One or both the following messages may appear in the system log:

  * PLATFORM-DIAGS-3-PUNT_FABRIC_DATA_PATH_FAILED
  * PLATFORM-DIAGS-0-LC_NP_LOOPBACK_FAILED

This vulnerability is documented as CSCtr26695and has been assigned 
Common Vulnerabilities and Exposures (CVE) ID CVE-2011-2549

Vulnerability Scoring Details
+----------------------------

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:

http://www.cisco.com/web/about/security/intelligence/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/cvss

* CSCtr26695 -  ASR9k:Line Card Issue with NP lockup

CVSS Base Score - 7.8
    Access Vector -            Network
    Access Complexity -        Low
    Authentication -           None
    Confidentiality Impact -   None
    Integrity Impact -         None
    Availability Impact -      Complete

CVSS Temporal Score - 6.8
    Exploitability -           Functional
    Remediation Level -        Official-Fix
    Report Confidence -        Confirmed

Impact
======

Successful exploitation of the vulnerability described in this
advisory may cause the affected line card to reload. Repeated
exploitation could result in a sustained denial of service (DoS)
condition.

Software Versions 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.

Each row of the Cisco IOS XR Software table (below) names a Cisco IOS
XR Software release train. If a given release train is vulnerable,
then the earliest possible releases that contain the fix, if
available at the time of Advisory, are listed in the "First Fixed
Release" column of the table.

+--------------------------------------------------------------------+
|    Major    |          Availability of Repaired Releases           |
|   Release   |                                                      |
|-------------+------------------------------------------------------|
|             | SMU ID  | SMU Name                     | First Fixed |
|             |         |                              | Release     |
|-------------+------------------------------------------------------|
| 3.2.X       |                                                      |
| through     | Not affected                                         |
| 4.0.X       |                                                      |
|-------------+------------------------------------------------------|
| 4.1.0       | AA05118 | asr9k-p-4.1.0.CSCtr26695.tar | 4.1.1       |
+--------------------------------------------------------------------+

Note: At the time of this advisory, Release 4.1.1 is expected to be
available on July 29, 2011.

Workarounds
===========

There are no workarounds for this vulnerability.

Obtaining Fixed Software
========================

Cisco has released free software updates that address these
vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html
Or as otherwise set forth at Cisco.com Downloads at:
http://www.cisco.com/public/sw-center/sw-usingswc.shtml

Do not contact psirt at cisco.com or security-alert at cisco.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 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 without Service Contracts
+----------------------------------

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)
  * e-mail: tac at cisco.com

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 TAC.

Refer to:
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
For additional TAC contact information, including 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 found during the resolution of multiple
customer service requests.

We would like to thank the Internet Measurement Group from the
University of Washington for their help and support on
troubleshooting this issue.

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-20110720-asr9k.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-announce at cisco.com
  * first-bulletins at lists.first.org
  * bugtraq at securityfocus.com
  * vulnwatch at vulnwatch.org
  * cisco at spot.colorado.edu
  * cisco-nsp at puck.nether.net
  * full-disclosure at lists.grok.org.uk
  * comp.dcom.sys.cisco at newsgate.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     | 2011-July-20     | 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/products/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/go/psirt

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Copyright 2010-2011 Cisco Systems, Inc. All rights reserved.
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