Summary

• A vulnerability in the SSH subsystem of the Cisco Nexus family of products could allow an authenticated, remote attacker to bypass authentication, authorization, and accounting (AAA) restrictions.
  
  The vulnerability is due to the improper processing of certain parameters that are passed to an affected device during the negotiation of an SSH connection. An attacker could exploit this vulnerability by authenticating to an affected device and passing a malicious value as part of the login procedure. A successful exploit could allow an attacker to bypass AAA restrictions and execute commands on the device command-line interface (CLI) that should be restricted to a different privileged user role.
  
  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-20161005-nxaaa

Affected Products

• Vulnerable Products

  The following Cisco products are vulnerable if they are running Cisco NX-OS System Software that is configured for AAA authentication and is accessible via SSH for IPv4 or IPv6.
  

  • Multilayer Director Switches
  • Nexus 1000V Series Switches
  • Nexus 2000 Series Fabric Extenders
  • Nexus 3000 Series Switches
  • Nexus 3500 Platform Switches
  • Nexus 4000 Series Switches
  • Nexus 5000 Series Switches
  • Nexus 5500 Platform Switches
  • Nexus 5600 Platform Switches
  • Nexus 6000 Series Switches
  • Nexus 7000 Series Switches
  • Nexus 7700 Series Switches
  • Nexus 9000 Series Switches in NX-OS mode

  Administrators can check the version of NX-OS Software running on their device by utilizing the show version command from the device CLI.  The following example identifies the 6.2(14) release:
  

  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) 2002-2015, 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 6.2(14)
    system:    version 6.2(14)
  .
  .
  . 

  
  

  Products Confirmed Not Vulnerable

  The following products are not affected by this vulnerability: 
  

  • Nexus 9000 Series Switches in Application Centric Infrastructure (ACI) mode
  • Unified Computing System (UCS) 6100 Series Fabric Interconnects
  • Unified Computing System (UCS) 6200 Series Fabric Interconnects

  No other Cisco products are currently known to be affected by 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: 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 consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories 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 Technical Assistance Center (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 should 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 that includes the following advisories:
  
  cisco-sa-20161005-bgp: Cisco NX-OS Border Gateway Protocol Denial of Service Vulnerability
  cisco-sa-20161005-dhcp1: Cisco NX-OS Software Crafted DHCPv4 Packet Denial of Service Vulnerability
  cisco-sa-20161005-dhcp2: Cisco NX-OS Software Malformed DHCPv4 Packet Denial of Service Vulnerability
  cisco-sa-20161005-nxaaa: Cisco NX-OS Software-Based Products Authentication, Authorization, and Accounting Bypass Vulnerability
  cisco-sa-20161005-otv: Cisco Nexus 7000 and 7700 Series Switches Overlay Transport Virtualization Buffer Overflow Vulnerability
  
  In the following table, the left column lists major releases of Cisco NX-OS Software. The center column indicates whether a major release is affected by the vulnerability described in this advisory and the first minor release that includes the fix for this vulnerability. The right column indicates whether a major release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.
  
  Cisco Nexus 1000 Series Switches : CSCuw79754
  
  

  Cisco NX-OS Software Major Release - Nexus 1000V Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability All Vulnerabilities Described in the Collection of Advisories
  Prior to 4.2	Affected; migrate to 5.2(1)SV3(1.10)	5.2(1)SV3(1.15)
  5.2	5.2(1)SV3(1.10)	5.2(1)SV3(1.15)

  
  Cisco Nexus 3000 and 3500 Series Switches :  CSCum35502
  
  

  Cisco NX-OS Software Major Release - Nexus 3000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 6.0	Affected; migrate to 6.0(2)U6(5a)	6.0(2)U6(7)
  6.0	6.0(2)U6(5a)	6.0(2)U6(7)
  7.0	7.0(3)I2(1a)	7.0(3)I4(1)

  
  

  Cisco NX-OS Software Major Release - Nexus 3500 Platform Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 6.0	Affected; migrate to 6.0(2)A6(5a)	6.0(2)A8(1)
  6.0	6.0(2)A6(5a)	6.0(2)A8(1)

  
  Cisco Nexus 4000 Series Switches : CSCuw78669
  
  

  Cisco NX-OS Software Major Release - Nexus 4000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  4.1	4.1(2)E1(1p)	4.1(2)E1(1p)

  
  Cisco Nexus 5000 Series Switches : CSCux88492
  
  

  Cisco NX-OS Software Major Release - Nexus 5000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 5.2	Affected; migrate to 5.2(1)N1(9a)	5.2(1)N1(9a)
  5.2	5.2(1)N1(9a)	5.2(1)N1(9a)

  
  Cisco Nexus 2000, 5500, 5600 and 6000 Series Switches : CSCux88492
  
  

  Cisco NX-OS Software  Major Release - Nexus 5500 Platform and 6000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 5.2	Affected; migrate to 5.2(1)N1(9a)	7.1(4)N1(1)
  5.2	5.2(1)N1(9a)	7.1(4)N1(1)
  6.0	Affected; migrate to  7.0(8)N1(1)	7.1(4)N1(1)
  7.0	7.0(8)N1(1)	7.1(4)N1(1)
  7.1	7.1(4)N1(1)	7.1(4)N1(1)
  7.2	7.2(2)N1(1)	7.2(2)N1(1)
  7.3	7.3(0)N1(1)	7.3(0)N1(1)

  
  Cisco Nexus 7000 and 7700 Series Switches : CSCum35502
  
  

  Cisco NX-OS Software Major Release - Nexus 7000 and 7700 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 5.2	Affected; migrate to 6.2(16)	7.2(2)D1(1)
  5.2	Affected; migrate to 6.2(16)	7.2(2)D1(1)
  6.0	Affected; migrate to 6.2(16)	7.2(2)D1(1)
  6.1	Affected; migrate to 6.2(16)	7.2(2)D1(1)
  6.2	6.2(16)	7.2(2)D1(1)
  7.2	7.2(2)D1(1)	7.2(2)D1(1)
  7.3	7.3(0)D1(1)	7.3(1)D1(1)

  
  Cisco Nexus 9000 Series Switches NX-OS Mode: CSCum35502
  
  

  Cisco NX-OS Software Major Release - Nexus 9000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  6.1	6.1(2)I3(3)	7.0(3)I4(1)
  7.0	7.0(3)I1(1)	7.0(3)I4(1)

  
  Cisco MDS 9000 Series Multilayer Switches : CSCum35502
  
  

  MDS Major Release - MDS	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of  Advisories
  5.2	Affected; migrate to 6.2(15)	6.2(15)
  6.2	6.2(15)	6.2(15)
  7.3	7.3(0)D1(1)	7.3(0)D1(1)

  
  Release Recommendations
  
  For additional assistance in determining the best NX-OS Software release for a Cisco Nexus Switch, refer to the recommended release document for the switch:
  

  • Cisco Multilayer Director Switches
  • Cisco Nexus 1000V for VMware Switches
  • 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 Switch

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-20161005-nxaaa

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2016-October-05

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