Summary

• A vulnerability in Cisco NX-OS Software running on Cisco Nexus 3000 Series Switches and Cisco Nexus 3500 Platform Switches could allow an unauthenticated, remote attacker to log in to the device with the privileges of the root user with bash shell access.
  
  The vulnerability is due to a user account that has a default and static password. This account is created at installation and cannot be changed or deleted without impacting the functionality of the system. An attacker could exploit this vulnerability by connecting to the affected system using this default account. The account can be used to authenticate remotely to the device via Telnet (or SSH on a specific release) and locally on the serial console.
  
  Cisco has released software updates that address this vulnerability. Workarounds that address this vulnerability are available.
  
  This advisory is available at the following link:
  
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-n3k

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Nexus 3000 Series Switches running Cisco NX-OS Software releases 6.0(2)U6(1), 6.0(2)U6(2), 6.0(2)U6(3), 6.0(2)U6(4), and 6.0(2)U6(5). There are no other vulnerable software releases for the Cisco Nexus 3000 Series Switch.
  
  This vulnerability affects Cisco Nexus 3500 Platform Switches running Cisco NX-OS Software releases 6.0(2)A6(1), 6.0(2)A6(2), 6.0(2)A6(3), 6.0(2)A6(4), 6.0(2)A6(5), and 6.0(2)A7(1). There are no other vulnerable software releases for the Cisco Nexus 3500 Platform Switch.
  
  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. The following example shows the output of this command for a Cisco Nexus 3000 Series Switch running Cisco NX-OS Software Release 6.0(2)U6(2):
  
  

  # 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 herein are owned by
  other third parties and are used and distributed under license.
  Some parts of this software are covered under the GNU Public
  License. A copy of the license is available at
  http://www.gnu.org/licenses/gpl.html.
  
  
  Software
    BIOS:      version 2.6.0
    loader:    version N/A
    kickstart: version 6.0(2)U6(2)
    system:    version 6.0(2)U6(2)
  .
  .
  .
  

  
  

  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 the following Cisco products:
  

  • Cisco Multilayer Director Switches
  • Cisco Nexus 1000 Series Switches
  • Cisco Nexus 2000 Series Switches
  • Cisco Nexus 4000 Series Switches
  • Cisco Nexus 5000 Series Switches
  • Cisco Nexus 5500 Platform Switches
  • Cisco Nexus 5600 Platform Switches
  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7700 Series Switches
  • Cisco Nexus 9000 Series Switches
  • Cisco Unified Computing System (UCS) 6100 Series Fabric Interconnects
  • Cisco UCS 6200 Series Fabric Interconnects

Workarounds

• For the following devices and Cisco NX-OS Software releases, this vulnerability is specific to remote access using Telnet or direct serial console access. A workaround to prevent exploitation via Telnet is to disable Telnet and use SSH for remote connections to the device. Note that no workaround is available for exploitation via direct serial console access.
  

  • Cisco Nexus 3000 Series Switches NX-OS Software Releases
    • 6.0(2)U6(1)
    • 6.0(2)U6(2)
    • 6.0(2)U6(3)
    • 6.0(2)U6(4)
    • 6.0(2)U6(5)
  • Cisco Nexus 3500 Platform Switches NX-OS Software Releases
    • 6.0(2)A6(2)
    • 6.0(2)A6(3)
    • 6.0(2)A6(4)
    • 6.0(2)A6(5)
    • 6.0(2)A7(1)

  The Telnet protocol is disabled by default on Nexus 3000 Series and 3500 Platform Switches. To determine whether the Telnet protocol is enabled, the administrative user can issue the show feature | incl telnet command:
  
  

  # show feature | incl telnet
  telnetServer          1          disabled
  

  
  Note: This workaround does not apply to Nexus 3500 Platform Switches running Cisco NX-OS Software release 6.0(2)A6(1) because the default account can be used with SSH remote access in this software release. Administrators of devices running 6.0(2)A6(1) are advised to upgrade to a fixed release.
  
  

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-20160302-n5ksnmp: Cisco NX-OS Software SNMP Packet Denial of Service Vulnerability
  • cisco-sa-20160302-netstack: Cisco NX-OS Software TCP Netstack Denial of Service Vulnerability
  • cisco-sa-20160302-n3k: Cisco Nexus 3000 Series and 3500 Platform Switches Insecure Default Credentials 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 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	Not affected	6.0(2)U6(5a) or later
  6.0	6.0(2)U6(1a) 6.0(2)U6(2a) 6.0(2)U6(3a) 6.0(2)U6(4a) 6.0(2)U6(5a)	6.0(2)U6(5a)
  7.0	Not affected	Not affected

  
  

  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	Not affected	6.0(2)A7(1a) or later
  6.0	6.0(2)A6(1a) 6.0(2)A6(2a) 6.0(2)A6(3a) 6.0(2)A6(4a) 6.0(2)A6(5a) 6.0(2)A7(1a)	6.0(2)A6(5a) or later 6.0(2)A7(1a) or later
  7.0	Not affected	Not affected

  
  
  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 Nexus 3000 Series and 3500 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 resolution of a customer case handled by the Cisco TAC.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-n3k

Revision History

• Version	Description	Section	Status	Date
  1.1	Updated the Workaround section to include more detailed information.	Workarounds	Final	2016-March-08
  1.0	Initial public release.	-	Final	2016-March-02

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