Summary

• A vulnerability in the Pong tool of Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition.
  
  The vulnerability exists because the affected software attempts to free the same area of memory twice. An attacker could exploit this vulnerability by sending a pong request to an affected device from a location on the network that causes the pong reply packet to egress both a FabricPath port and a non-FabricPath port. An exploit could allow the attacker to cause a dual or quad supervisor virtual port-channel (vPC) to reload.
  
  Note: This vulnerability is exploitable only when all of the following are true:
  

  1. The Pong tool is enabled on an affected device. The Pong tool is disabled in NX-OS by default.
  2. The FabricPath feature is enabled on an affected device. The FabricPath feature is disabled in NX-OS by default.
  3. A FabricPath port is actively monitored via a Switched Port Analyzer (SPAN) session. SPAN sessions are not configured or enabled in NX-OS by default.

  
  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
  
  This advisory is available at the following link:
  https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180117-nx-os

Affected Products

• Vulnerable Products

  This vulnerability affects the following products when running Cisco NX-OS Software Release 7.2(1)D(1), 7.2(2)D1(1), or 7.2(2)D1(2) with both the Pong and FabricPath features enabled and the FabricPath port is actively monitored via a SPAN session:
  

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7700 Series Switches

  To determine whether a device is running a vulnerable release of Cisco NX-OS Software, administrators can use the show version command in the NX-OS command-line interface (CLI).
  
  The following example shows the output of the show version command for a Cisco Nexus 7000 Series Switch running Cisco NX-OS Software Release 7.2(2)D1(2):
  

  Nexus# show version
  Cisco Nexus Operating System (NX-OS) Software
  TAC support: http://www.cisco.com/tac
  Documents: http://www.cisco.com/en/US/products/ps9372/tsd_products_support_series_home.html
  Copyright (c) 2002-2016, Cisco Systems, Inc. All rights reserved.
  The copyrights to certain works contained in this software are
  owned by other third parties and used and distributed under
  license. Certain components of this software are licensed under
  the GNU General Public License (GPL) version 2.0 or the GNU
  Lesser General Public License (LGPL) Version 2.1. A copy of each
  such license is available at
  http://www.opensource.org/licenses/gpl-2.0.php and
  http://www.opensource.org/licenses/lgpl-2.1.php
  
  Software
    BIOS:      version 2.12.0
    kickstart: version 7.2(2)D1(2)
    system:    version 7.2(2)D1(2)
  .
  .
  .

  To determine whether a device has the Pong tool enabled, administrators can use the show running-config | include "feature pong" command in the NX-OS CLI. The following example shows the output of this command for a Cisco Nexus 7000 Series Switch that has the Pong tool enabled (if this command returns empty output the Pong tool is not enabled):
  

  Nexus# show running-config | include "feature pong"
  feature pong

  To determine whether a device has the FabricPath feature enabled, administrators can use the show running-config | include "feature-set fabricpath" command in the NX-OS CLI. The following example shows the output of this command for a Cisco Nexus 7000 Series Switch that has the FabricPath feature enabled (if this command returns empty output, the FabricPath feature is not enabled):
  

  Nexus# show running-config | include "feature-set fabricpath"
  feature-set fabricpath

  To determine whether a device has a SPAN session configured, administrators can use the show running-config monitor command in NX-OS CLI. The following example shows the output of this command for a Cisco Nexus 7000 Series Switch that has a SPAN session monitoring interface Ethernet 1/10 configured and enabled (if this command returns empty output, no SPAN session is configured):
  

  Nexus# show running-config monitor
  
  !Command: show running-config monitor
  !Time: Mon Oct  9 12:04:52 2017
  
  version 7.2(2)D1(2)
  monitor session 1 
    source interface Ethernet1/10 both
    destination interface Ethernet1/12
    no shut

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.
  
  Cisco has confirmed that this vulnerability does not affect Cisco NX-OS Software Releases 7.2(0)D1(1) and earlier.
  
  Cisco has confirmed that this vulnerability does not affect Cisco Multilayer Director Switches as the affected NX-OS releases are not available for this platform.

Details

• The Pong tool utilizes synchronized clocks on the network to measure real-time latency. Latency is the delay of the network between any two points as seen by a frame traveling between the two points. Pong measures port-to-port delays and is similar to the network-monitoring utility Ping but provides for a greater depth of network diagnostics.

Indicators of Compromise

• Exploitation of this vulnerability will cause an affected device to reload and generate a pong core file. Contact the Cisco Technical Assistance Center (TAC) to review the core file and determine whether the device has been compromised by exploitation of this vulnerability.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
  https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

  Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.

  In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

  Customers Without Service Contracts

  Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
  https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

  Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

  Fixed Releases

  This vulnerability is fixed in Cisco NX-OS Software Releases 7.3(0)D1(1) and later.

  The software can be downloaded from the Software Center on Cisco.com by navigating to Products > Switches > Data Center Switches > Nexus 7000 Series Switches.

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Source

• This vulnerability was found during the resolution of a Cisco TAC support case.

URL

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180117-nx-os

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2018-January-17

  Show Less