Summary

• A vulnerability in the CLI of Cisco IOS XE SD-WAN Software could allow an authenticated, local attacker to overwrite arbitrary files in the underlying file system.

  This vulnerability is due to insufficient validation of the parameters of a specific CLI command. An attacker could exploit this vulnerability by issuing that command with specific parameters. A successful exploit could allow the attacker to overwrite the content of any arbitrary file that resides on the underlying host file system.

  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-iosxe-arbfile-FUxskKDE

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco IOS XE SD-WAN Software and had the SD-WAN feature enabled. The SD-WAN feature is not enabled by default.

  • 1000 Series Integrated Services Routers (ISRs)
  • 4000 Series ISRs
  • ASR 1000 Series Aggregation Services Routers
  • Cloud Services Router 1000V Series

  For information about which Cisco software releases were vulnerable at the time of publication, see the Fixed Software section of this advisory.

  Determine the Device Configuration

  There are two methods for determining whether the SD-WAN feature is enabled on a device:

  Option 1: Use the show running-config | include sdwan Command
  

  To determine whether sdwan mode is enabled on a device, use the show running-config | include sdwan command and check the tunnel mode in the output. If the command returns tunnel mode sdwan, the sdwan feature is enabled and the device is vulnerable. If the command returns no output or the command does not exist, the SD-WAN feature is not enabled and the device is not affected by this vulnerability.

  The following example shows the output of the show running-config | include sdwan command on a device that has the SD-WAN feature enabled:

  Router# show running-config | include sdwan
  tunnel mode sdwan
  Router#

  Option 2: Use the show version Command
  

  Alternatively, use the show version command to determine whether the Cisco IOS XE device is in Controller mode. The end of the output includes the router operating mode, which indicates whether the device is in Controller mode.

  The following example shows part of the show version command output on a device that has the SD-WAN feature enabled:

  Router# show version
  .
  .
  .
  Router operating mode: Controller-Managed
  .
  .
  .

  
  

  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

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 during the resolution of a Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-arbfile-FUxskKDE

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2021-MAR-24

  Show Less