Summary

• A vulnerability in a specific CLI command implementation of Cisco Nexus 9000 Series ACI Mode Switch Software could allow an authenticated, local attacker to escape a restricted shell on an affected device.
  
  The vulnerability is due to insufficient sanitization of user-supplied input when issuing a specific CLI command with parameters on an affected device. An attacker could exploit this vulnerability by authenticating to the device CLI and issuing certain commands. A successful exploit could allow the attacker to escape the restricted shell and execute arbitrary commands with root-level privileges on the affected device.
  

  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-aci-shell-escape

  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 only affects Cisco Nexus 9000 Series ACI Mode Switches that are running a release prior to 13.2(4d).

  Determining the Cisco NX-OS Software Release

  Administrators can determine the release of Cisco NX-OS Software running on a device by using the show version command in the device CLI. The following example identifies the 11.2(2) Release:

  nxos-n9k-aci# show version
  Cisco Nexus Operating System (NX-OS) Software
  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 N/A
  kickstart: version 11.2(2) [build 11.2(1.184)]
  system:    version 11.2(2) [build 11.2(1.184)]
  .
  .
  .

  Determining the Cisco Application Policy Infrastructure Controller Software Release

  There is a one-to-one mapping between the software for Cisco Application Policy Infrastructure Controller (APIC) and Cisco Nexus 9000 Series Fabric Switches in ACI mode. To determine which Cisco APIC Software release is running on a device, administrators can disregard the leftmost digit of the Cisco NX-OS Software version number. In the preceding example, the output shows Cisco NX-OS Software version 11.2(2), which maps to Cisco APIC Software Release 1.2(2).

  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 determined 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 Director Switches
  • Nexus 1000V Switch for Microsoft Hyper-V
  • Nexus 1000V Switch for VMware vSphere
  • Nexus 2000 Series Fabric Extenders
  • Nexus 3000 Series Switches
  • Nexus 3500 Platform Switches
  • Nexus 3600 Platform Switches
  • Nexus 5000 Series Switches
  • Nexus 5500 Platform Switches
  • Nexus 5600 Platform Switches
  • Nexus 7000 Series Switches
  • Nexus 7700 Series Switches
  • Nexus 9000 Series Switches in standalone NX-OS mode
  • 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

  This vulnerability is fixed in Cisco Nexus 9000 Series ACI Mode Switch Software Releases 13.2(4d) and later.

  The recommended action for all Cisco customers running a device with an affected version is to upgrade to the latest maintenance or latest long-lived version. Cisco suggests that customers visit the following page to determine what fixed release to choose: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/recommended-release/b_Recommended_Cisco_ACI_Releases.html.

  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

• Cisco would like to thank Nicolas Biscos and Gaetan Ferry from Synacktiv for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190306-aci-shell-escape

Revision History

• Version	Description	Section	Status	Date
  1.1	Updated first fixed software release.	Vulnerable Products, Fixed Software	Final	2019-March-19
  1.0	Initial public release.	—	Final	2019-March-06

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