Summary

• A vulnerability in the file system on the pluggable USB 3.0 Solid State Drive (SSD) for Cisco IOS XE Software could allow an authenticated, physical attacker to remove the USB 3.0 SSD and modify sensitive areas of the file system, including the namespace container protections.

  The vulnerability occurs because the USB 3.0 SSD control data is not stored on the internal boot flash. An attacker could exploit this vulnerability by removing the USB 3.0 SSD, modifying or deleting files on the USB 3.0 SSD by using another device, and then reinserting the USB 3.0 SSD on the original device. A successful exploit could allow the attacker to remove container protections and perform file actions outside the namespace of the container with root privileges.

  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-iox-usb-guestshell-WmevScDj

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco Catalyst 9300 Series Switches and Cisco Catalyst 9500 Series Switches if they were running a vulnerable release of Cisco IOS XE Software with the IOx Guest Shell enabled and a USB 3.0 SSD installed.

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

  Determine the Device Configuration

  To determine whether the device has a vulnerable configuration, assess the IOx Guest Shell and USB 3.0 SSD status.

  Determine Whether the IOx Guest Shell Is Enabled

  To determine whether the IOx Guest Shell is enabled, use the show app-hosting list privileged command. The following command output shows a device with the IOx Guest Shell enabled:

  Device# show app-hosting list 
  
  App id                           State
  ------------------------------------------------------
  guestshell                       RUNNING

  Determine Whether a USB 3.0 SSD Drive Is Installed

  To determine whether a USB 3.0 SSD pluggable drive is installed, use the show inventory | include usbflash* CLI command. If output is returned, the drive is installed.

  9300# show inventory | include usbflash*
  NAME: "usbflash1", DESCR: "usbflash1" PID: SSD-120G , VID: STP21460FN9, SN: V01

  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:

  • IOS Software
  • IOS XR Software
  • NX-OS Software

Details

• The Cisco Catalyst 9300 and 9500 Series Switches have a USB 3.0 SSD port on the rear panel of the switch. This port supports an optional 120GB USB 3.0 SSD storage device (SSD-120G). SSD-120G provides an extra 120GB of storage for application hosting. Applications can be hosted in Kernel-based Virtual Machines (KVMs), Linux Containers (LXCs), or Docker containers. SSD-120G can also be used to save packet captures, trace logs generated by the operating system, Graceful Insertion and Removal (GIR) snapshots, and third-party applications. SSD-120G can be used simultaneously as a general-purpose storage device and as an application-hosting device. Administrators must use only Cisco USB drives; non-Cisco USB drives are not supported. SSD-120G is enabled with Self-Monitoring, Analysis and Reporting Technology (S.M.A.R.T.) functionality to monitor endurance, predict wear out, and perform various self-tests.

  For additional information, see USB 3.0 SSD Overview in the Cisco Catalyst 9300 Series Switches Hardware Installation Guide.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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.

  Cisco IOS and IOS XE Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).

  Customers can use the Cisco Software Checker to search advisories in the following ways:

  • Choose the software and one or more releases
  • Upload a .txt file that includes a list of specific releases
  • Enter the output of the show version command

  After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.

  Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S:

  By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search.

  For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.

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 by Victor Kamensky of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iox-usb-guestshell-WmevScDj

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2020-SEP-24

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