Summary

• A vulnerability in the Border Gateway Protocol (BGP) implementation of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to the device unexpectedly reloading.

  The vulnerability is due to incomplete input validation of the BGP update messages. An attacker could exploit this vulnerability by sending a crafted BGP update message to the targeted device. An exploit could allow the attacker to cause the switch to reload unexpectedly.

  The Cisco implementation of the BGP protocol only accepts incoming BGP traffic from explicitly defined peers. To exploit this vulnerability, an attacker must be able to send the malicious packets over a TCP connection that appears to come from a trusted BGP peer or inject malformed messages into the victim's BGP network. This would require obtaining information about the BGP peers in the affected system's trusted network.

  The vulnerability may be triggered when the router receives a malformed BGP message from a peer on an existing BGP session. At least one BGP neighbor session must be established for a router to be vulnerable.

  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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-nxosbgp

  This advisory is part of the June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection, which includes 24 Cisco Security Advisories that describe 24 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection.

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco NX-OS Software:

  • Nexus 2000 Series Switches
  • Nexus 3000 Series Switches
  • Nexus 3500 Platform Switches
  • Nexus 3600 Platform Switches
  • Nexus 5500 Platform Switches
  • Nexus 5600 Platform Switches
  • Nexus 6000 Series Switches
  • Nexus 7000 Series Switches
  • Nexus 7700 Series Switches
  • Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode
  • Nexus 9000 Series Switches in standalone NX-OS mode
  • Nexus 9500 R-Series Line Cards and Fabric Modules

  For information about which Cisco NX-OS Software releases are vulnerable, see the Fixed Software section of this advisory.

  Determining if the NX-OS Software Is Vulnerable

  The vulnerability affects only NX-OS devices configured with BGP functionality. In addition, the device needs to have at least one BGP neighbor (peer) configured. The potentially malicious BGP peer needs to be configured on the NX-OS device as a BGP neighbor. This vulnerability applies to BGP traffic destined for the device. The device processes BGP packets on TCP port 179 on IP version 4 (IPv4) and IP version 6 (IPv6).

  To determine whether a Nexus device is configured with the BGP feature and a BGP neighbor, administrators can use the show running-config | include "router bgp" and show running-config | include "neighbor" commands from the NX-OS CLI and verify that the feature is enabled.

  The following example shows the BGP feature enabled with one BGP neighbor on a device running NX-OS Software:

  nxos-switch# show running-config | include "router bgp"
  router bgp 64512
  
  nxos-switch# show running-config | include "neighbor"
  neighbor 209.165.201.1 remote-as 64497

  Determining the Cisco NX-OS Software Release

  Administrators can check the release of Cisco NX-OS Software that is running on a device by using the show version command in the device CLI. The following example shows the output of this command on a device that is running Cisco NX-OS Software Release 7.3(2)D1(1):

  nxos-switch# 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) 2002-2017, 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 7.3(2)D1(1)
    system:    version 7.3(2)D1(1)
  .
  .
  .
  

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect the following Cisco products:

  • Firepower 2100 Series
  • Firepower 4100 Series Next-Generation Firewall
  • Firepower 9300 Security Appliance
  • MDS 9000 Series Multilayer Switches
  • Nexus 1000V Series Switches
  • Nexus 1100 Series Cloud Services Platforms
  • UCS 6100 Series Fabric Interconnects
  • UCS 6200 Series Fabric Interconnects
  • UCS 6300 Series Fabric Interconnects

  Cisco has not investigated whether this vulnerability affects Cisco Nexus 4000 Series Switches, Cisco Nexus 5010 Switches, or Cisco Nexus 5020 Switches because those products have reached end-of-life status. For more information, refer to the End-of-Sale and End-of-Life Announcement for the Cisco Nexus 4000 Series Switch Modules for IBM BladeCenter and the End-of-Sale and End-of-Life Announcement for the Cisco Nexus 5010 and Nexus 5020 Switches.

Workarounds

• There are no workarounds that address this vulnerability. However, BGP Neighbor Authentication with MD5 can help to ensure that the configured BGP peer is not spoofed.
  
  Configuring BGP Neighbor Authentication with MD5
  
  BGP can be configured to authenticate route updates from peers using MD5 digests. To configure BGP to use MD5 authentication, use the following commands in the neighbor configuration mode CLI:

  switch(config)# router bgp 65536
  switch(config-router-neighbor)# password BGPpassword

  Please refer to the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide for additional information.

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: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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 upgrade 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: http://www.cisco.com/en/US/support/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

  Customers are advised to upgrade to an appropriate release as indicated in the applicable table in this section. To help ensure a complete upgrade solution, consider that this advisory is part of a collection. For a complete list of the advisories in the collection and links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection.

  In the following tables, the left column lists releases of Cisco FXOS or NX-OS Software. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.

  Nexus 3000 Series Switches: CSCve91387

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  Prior to 7.0(3)I4	7.0(3)I4(7)	7.0(3)I7(4)
  7.0(3)I4	7.0(3)I4(7)	7.0(3)I7(4)
  7.0(3)I5	7.0(3)I6(2)	7.0(3)I7(4)
  7.0(3)I6	7.0(3)I6(2)	7.0(3)I7(4)
  7.0(3)I7	Not vulnerable	7.0(3)I7(4)

  Nexus 3500 Platform Switches: CSCve91371

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  6.0	6.0(2)A8(7)	7.0(3)I7(4)
  7.0.3	7.0(3)I7(2)	7.0(3)I7(4)

  Nexus 2000, 5500, 5600, and 6000 Series Switches: CSCve79599

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  6.0	7.1(5)N1(1)	7.3(3)N1(1)
  7.0	7.1(5)N1(1)	7.3(3)N1(1)
  7.1	7.1(5)N1(1)	7.3(3)N1(1)
  7.2	7.3(3)N1(1)	7.3(3)N1(1)
  7.3	7.3(3)N1(1)	7.3(3)N1(1)

  Nexus 7000 and 7700 Series Switches: CSCve79599 and CSCve87784

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  6.2	6.2(20)	8.1(2) or 8.2(1)
  7.2	7.3(2)D1(1)	8.1(2) or 8.2(1)
  7.3	7.3(2)D1(1)	8.1(2) or 8.2(1)
  8.0	8.1(2)	8.1(2) or 8.2(1)
  8.1	8.1(2)	8.1(2) or 8.2(1)
  8.2	8.2(1)	8.1(2) or 8.2(1)

  Nexus 9000 Series Fabric Switches in ACI mode: CSCve87784

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  Prior to 12.1/2.1	12.1(3h)/2.1(3h)	13.1(1i)/3.1(1i)
  12.1/2.1	12.1(3h)/2.1(3h)	13.1(1i)/3.1(1i)
  12.2/2.2	12.2(3j)/2.2(3j)	13.1(1i)/3.1(1i)
  12.3/2.3	13.0(1k)/3.0(1k)	13.1(1i)/3.1(1i)
  13.0/3.0	13.0(1k)/3.0(1k)	13.1(1i)/3.1(1i)
  13.1/3.1	Not vulnerable	13.1(1i)/3.1(1i)

  Nexus 9000 Series Switches in standalone NX-OS mode: CSCve91387 and CSCve87784

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  Prior to 7.0(3)I4	7.0(3)I4(7)	7.0(3)I7(4)
  7.0(3)I4	7.0(3)I4(7)	7.0(3)I7(4)
  7.0(3)I5	7.0(3)I6(2)	7.0(3)I7(4)
  7.0(3)I6	7.0(3)I6(2)	7.0(3)I7(4)
  7.0(3)I7	Not vulnerable	7.0(3)I7(4)

  Nexus 9500 R-Series Line Cards and Fabric Modules and Nexus 3600 Platform Switches: CSCve79599

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
  7.0	7.0(3)F2(2)	7.0(3)F3(3a)

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 resolution of a TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-nxosbgp

Revision History

• Version	Description	Section	Status	Date
  1.1	CSCve87784 added for Nexus 7000 and 9000 platforms.	Fixed Software	Final	2022-SEP-22
  1.0	Initial public release.	-	Final	2018-JUN-20

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