Summary

• A vulnerability in the 802.1X implementation for Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device.

  The vulnerability is due to incomplete input validation of Extensible Authentication Protocol over LAN (EAPOL) frames. An attacker could exploit this vulnerability by sending a crafted EAPOL frame to an interface on the targeted device. A successful exploit could allow the attacker to cause the Layer 2 (L2) forwarding process to restart multiple times, leading to a system-level restart of the device and a DoS condition.
  
  Note: This vulnerability affects only NX-OS devices configured with 802.1X functionality.

  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-20190306-nx-os-lan-auth

  This advisory is part of the March 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication, which includes 25 Cisco Security Advisories that describe 26 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: March 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.
  

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco NX-OS Software and have 802.1X functionality enabled:

  • Nexus 1000V Switch for VMware vSphere
  • Nexus 2000 Series Fabric Extenders
  • Nexus 3000 Series Switches¹
  • Nexus 3500 Platform Switches¹
  • 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 mode¹

  ¹The Nexus 3000, 3500, and 9000 devices did not support 802.1X functionality until the 7.0(3)I7 release.

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

  Determining the 802.1X Configuration

  This vulnerability affects only NX-OS devices configured with 802.1X functionality. If 802.1X is not enabled or supported on an interface, the Cisco NX-OS device drops any EAPOL frames.

  Administrators can determine whether a Nexus device is configured for 802.1X on an interface by using the show dot1x interface Ethernet slot / port command from the NX-OS CLI. If the command returns output, the interface is configured for 802.1X:

  nxos-switch# showdot1x interface Ethernet1/2
  Dot1x Info for Ethernet1/2
  -----------------------------------
  PAE = AUTHENTICATOR
  PortControl = FORCE_AUTH
  HostMode = SINGLE HOST
  ReAuthentication = Disabled
  QuietPeriod = 60
  ServerTimeout = 30
  SuppTimeout = 30
  ReAuthPeriod = 3600 (Locally configured)
  ReAuthMax = 2
  MaxReq = 2
  TxPeriod = 30
  RateLimitPeriod = 0
  InactivityPeriod = 0
  Mac-Auth-Bypass = Disabled

  For additional information, administrators can refer to the Configuring 802.1X chapter of the Cisco NX-OS Security Configuration Guide.

  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 7.0(3)I5(1):

  nxos-switch# show version
  Cisco Nexus Operating System (NX-OS) Software
  TAC support: http://www.cisco.com/tac
  Copyright (C) 2002-2016, Cisco and/or its affiliates.
  All rights reserved.
  The copyrights to certain works contained in this software are
  owned by other third parties and used and distributed under their own
  licenses, such as open source.  This software is provided "as is," and
  unless otherwise stated, there is no warranty, express or implied, 
  including but not limited to warranties of merchantability and fitness 
  for a particular purpose. Certain components of this software are 
  licensed under the GNU General Public License (GPL) version 2.0 or 
  GNU General Public License (GPL) version 3.0  or the GNU
  Lesser General Public License (LGPL) Version 2.1 or 
  Lesser General Public License (LGPL) Version 2.0. 
  A copy of each such license is available at
  http://www.opensource.org/licenses/gpl-2.0.php and
  http://opensource.org/licenses/gpl-3.0.html and
  http://www.opensource.org/licenses/lgpl-2.1.php and
  http://www.gnu.org/licenses/old-licenses/library.txt.
  Software
    BIOS: version 07.57
    NXOS: version 7.0(3)I5(1) [build 7.0(3)I5(0.9)]
    BIOS compile time:  06/29/2016
    NXOS image file is: bootflash:///nxos.7.0.3.I5.0.9.bin
    NXOS compile time:  8/1/2016 23:00:00 [08/02/2016 00:30:32]
    .
    .
    .

  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 Firewalls
  • Firepower 4100 Series Next-Generation Firewalls
  • Firepower 9300 Security Appliance
  • MDS 9000 Series Multilayer Switches
  • Nexus 1000V Switch for Microsoft Hyper-V
  • Nexus 3600 Platform Switches
  • Nexus 9500 R-Series Line Cards and Fabric Modules
  • UCS 6200 Series Fabric Interconnects
  • UCS 6300 Series Fabric Interconnects
  • UCS 6400 Series Fabric Interconnects

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

  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, customers should consider that this advisory is part of a bundled publication. The following page provides a complete list of bundle advisories: Cisco Event Response: March 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

  In the following tables, the left column lists releases of Cisco FXOS Software or Cisco 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 bundle and which release includes fixes for those vulnerabilities.

  Although the releases listed in the right column of each table include fixes for the vulnerabilities, the fix related to the Cisco NX-OS Software Image Signature Verification Vulnerability requires a BIOS upgrade as part of the software upgrade. Customers who are upgrading the software for any of the following products are advised to refer to this advisory for further details about the BIOS upgrade and affected product IDs and BIOS versions:

  • Nexus 3000 Series Switches
  • Nexus 9000 Series Fabric Switches in ACI mode
  • Nexus 9000 Series Switches in standalone NX-OS mode
  • Nexus 9500 R-Series Line Cards and Fabric Modules

  Nexus 1000V Switch for VMware vSphere: CSCvj22447

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 5.2	5.2(1)SV3(1.4b)	5.2(1)SV3(4.1a)
  5.2	5.2(1)SV3(1.4b) 5.2(1)SV3(4.1)	5.2(1)SV3(4.1a)

  Nexus 3000 Series Switches: CSCvj22446

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 7.0(3)I4	Not vulnerable	7.0(3)I7(6)
  7.0(3)I4	Not vulnerable	7.0(3)I7(6)
  7.0(3)I5	Not vulnerable	7.0(3)I7(6)
  7.0(3)I6	Not vulnerable	7.0(3)I7(6)
  7.0(3)I7	7.0(3)I7(4)	7.0(3)I7(6)
  9.2	Not vulnerable	9.2(2)

  Nexus 3500 Platform Switches: CSCvj22446

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 6.0(2)A8	Not vulnerable	6.0(2)A8(11)
  6.0(2)A8	Not vulnerable	6.0(2)A8(11)
  7.0(3)I7	7.0(3)I7(4)	7.0(3)I7(6)
  9.2	Not vulnerable	9.2(2)

  Nexus 2000, 5500, 5600, and 6000 Series Switches: CSCvj22449

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 5.2	7.1(5)N1(1b)	7.1(5)N1(1b)
  5.2	7.1(5)N1(1b)	7.1(5)N1(1b)
  6.0	7.1(5)N1(1b)	7.1(5)N1(1b)
  7.0	7.1(5)N1(1b)	7.1(5)N1(1b)
  7.1	7.1(5)N1(1b)	7.1(5)N1(1b)
  7.2	7.3(5)N1(1)	7.3(5)N1(1)
  7.3	7.3(5)N1(1)	7.3(5)N1(1)

  Nexus 7000 and 7700 Series Switches: CSCvi93959

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  6.2	6.2(20a)	6.2(22)
  7.2	7.3(3)D1(1)	6.2(22)
  7.3	7.3(3)D1(1)	8.2(3)
  8.0	8.2(3)	8.2(3)
  8.1	8.2(3)	8.2(3)
  8.2	8.2(3)	8.2(3)
  8.3	8.3(1)	8.3(2)

  Nexus 9000 Series Fabric Switches in ACI Mode: CSCvj22443

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 13.1	13.2(1l)	14.0(3d)
  13.1	13.2(1l)	14.0(3d)
  13.2	13.2(1l)	14.0(3d)
  14.0	Not vulnerable	14.0(3d)

  Nexus 9000 Series Switches in Standalone NX-OS Mode: CSCvj22446

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Prior to 7.0(3)I4	Not vulnerable	7.0(3)I7(6)
  7.0(3)I4	Not vulnerable	7.0(3)I7(6)
  7.0(3)I5	Not vulnerable	7.0(3)I7(6)
  7.0(3)I6	Not vulnerable	7.0(3)I7(6)
  7.0(3)I7	7.0(3)I7(4)	7.0(3)I7(6)
  9.2	Not vulnerable	9.2(2)

  
  

  Additional Resources

  For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, administrators can refer to the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco MDS Series Switches
  Cisco Nexus 1000V for VMware Switch
  Cisco Nexus 3000 Series and 3500 Series Switches
  Cisco Nexus 5000 Series Switches
  Cisco Nexus 5500 Platform Switches
  Cisco Nexus 6000 Series Switches
  Cisco Nexus 7000 Series Switches
  Cisco Nexus 9000 Series Switches
  Cisco Nexus 9000 Series ACI-Mode Switches

  For help determining the best Cisco NX-OS Software release for Cisco UCS, refer to the Recommended Releases documents in the release notes for the device.

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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190306-nx-os-lan-auth

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2019-March-06

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