Summary

• A vulnerability in the Image Signature Verification feature of Cisco NX-OS Software could allow an authenticated, local attacker with administrator-level credentials to install a malicious software image on an affected device.
  
  The vulnerability is due to improper verification of digital signatures for software images. An attacker could exploit this vulnerability by loading an unsigned software image on an affected device. A successful exploit could allow the attacker to boot a malicious software image.

  Note: The fix for this vulnerability requires a BIOS upgrade as part of the software upgrade. For additional information, see the Details section of this advisory.

  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-nxos-sig-verif

  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 Cisco products that are listed in the following subsection when the product meets all the following conditions:

  • Has a particular product ID (PID)
  • Is running an affected BIOS version
  • Is running a vulnerable release of Cisco NX-OS Software

  To help customers identify device characteristics that could indicate a vulnerable device, this advisory provides details about determining the device’s PID, the running BIOS version, and the running Cisco NX-OS Software release.

  Affected Cisco Products

  • Nexus 3000 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

  Affected Product IDs and BIOS Versions

  The tables in this section provide details about the affected PIDs of the Cisco products that are affected by the vulnerability described in this advisory. PIDS that are not shown in these tables are not known to be affected by this vulnerability. BIOS versions prior to the first fixed version are affected by this vulnerability.

  Nexus 3000 Series Switches

  Nexus 3000 PID	First Fixed BIOS Version
  N3K-C31128PQ-10GE	7.63
  N3K-C3132C-Z N3K-C3164Q-40GE N3K-C3232C N3K-C3264Q	8.34

  
  

  Nexus 9000 Series Fabric Switches in ACI Mode and Nexus 9000 Series Switches in Standalone NX-OS Mode

  Nexus 9000 PID	First Fixed BIOS Version
  N9K-C92160YC-X N9K-C92304QC N9K-C9232C N9K-C9236C N9K-C9272Q N9K-C93108TC-EX N9K-C93120TX N9K-C93128TX N9K-C93180YC-EX N9K-C9332PQ N9K-C9372PX N9K-C9372PX-E N9K-C9372TX N9K-C9372TX-E N9K-C9396PX N9K-C9396TX	7.63
  N9K-SUP-A N9K-SUP-B	8.34

  
  

  Nexus 9500 R-Series Line Cards and Fabric Modules

  Nexus 9500 PID	First Fixed BIOS Version
  N9K-SUP-B	8.34

  
  

  Affected Cisco NX-OS Software Releases

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

  Determining the Cisco NX-OS Product ID

  Administrators can check the product ID of a device by using the show inventory command in the device CLI. The following example shows the output of the command for a device that has the PID N3K-C3232C:

  switch# show inventory
  NAME: "Chassis",  DESCR: "Nexus3000 C3232C Chassis"              
  PID: N3K-C3232C          ,  VID: V02 ,  SN: FOC20291JA0    
        
  NAME: "Slot 1",  DESCR: "32x40/100G QSFP28 2x10G SFP+ Ethernet Module"
  PID: N3K-C3232C          ,  VID: V02 ,  SN: FOC20291JA0          
  
  NAME: "Power Supply 1",  DESCR: "Nexus3000 C3232C Chassis Power Supply" 
  PID: NXA-PAC-650W-PI     ,  VID: V01 ,  SN: LIT20362Z6G    

  Determining the Cisco NX-OS BIOS Version

  Administrators can check the Cisco NX-OS BIOS version that is running on a device by using the show version command in the device CLI. The following example shows the output of the command for a device that is running Cisco NX-OS BIOS version 8.32:

  N9K-A# show version 
  Cisco Nexus Operating System (NX-OS) Software
  <snip>
  .
  .
  .
  Software
    BIOS: version 08.32

  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 1000V Switch for VMware vSphere
  • Nexus 2000 Series Fabric Extenders
  • 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
  • UCS 6200 Series Fabric Interconnects
  • UCS 6300 Series Fabric Interconnects
  • UCS 6400 Series Fabric Interconnects

Details

• The fix for this vulnerability requires a BIOS upgrade, which will be installed when upgrading to a fixed Cisco NX-OS Software release by using the install all command. The install all command for software upgrades performs configuration compatibility checks and BIOS upgrades automatically. The Cisco NX-OS Software upgrade documentation provides more information about upgrading the BIOS and using the install all command:

  Cisco Nexus 3000 Series NX-OS Software Upgrade and Downgrade Guide, Release 9.x
  Cisco Nexus 9000 Series NX-OS Software Upgrade and Downgrade Guide, Release 9.x

  Note: Customers who are running a vulnerable PID with a fixed software release may not have upgraded the BIOS when the software was installed. Customers are advised to confirm that the BIOS is running a fixed BIOS version (first fixed or later).

  The Determining the Cisco NX-OS BIOS Version section of this advisory provides information about checking the installed BIOS version.

  Trust Center Downloads provides methods to determine the authenticity of Cisco software image files.

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 this advisory requires a BIOS upgrade as part of the software upgrade. Customers who are upgrading the software for any of the products listed in this section are advised to review this entire advisory for further details about the BIOS upgrade and affected product IDs and BIOS versions.

  Nexus 3000 Series Switches: CSCvj14135

  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	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I4	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I5	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I6	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I7	7.0(3)I7(5)	7.0(3)I7(6)
  9.2(1)	Not vulnerable	9.2(2)

  Nexus 9000 Series Fabric Switches in ACI Mode: CSCvk70903

  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	Not vulnerable	14.0(3d)
  14.0	Not vulnerable	14.0(3d)

  Nexus 9000 Series Switches in Standalone NX-OS Mode: CSCvj14135

  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	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I4	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I5	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I6	7.0(3)I7(5)	7.0(3)I7(6)
  7.0(3)I7	7.0(3)I7(5)	7.0(3)I7(6)
  9.2	Not vulnerable	9.2(2)

  Nexus 9500 R-Series Line Cards and Fabric Modules: CSCvk70905

  Cisco NX-OS Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  7.0(3)F1	7.0(3)F3(5)	7.0(3)F3(5)
  7.0(3)F2	7.0(3)F3(5)	7.0(3)F3(5)
  7.0(3)F3	7.0(3)F3(5)	7.0(3)F3(5)
  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 internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190306-nxos-sig-verif

Revision History

• Version	Description	Section	Status	Date
  1.2	Updated Vulnerable Products section to include PID - N3K-C3232C.	Vulnerable Products	Final	2019-April-15
  1.1	Updated the fixed software table for Nexus 9000 (in standalone NX-OS mode) for software releases prior to 7.0(3)I4.	Fixed Software	Final	2019-March-19
  1.0	Initial public release.	—	Final	2019-March-06

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