Summary

• A vulnerability in task group assignment for a specific CLI command in Cisco IOS XR Software could allow an authenticated, local attacker to execute that command, even though administrative privileges should be required. The attacker must have valid credentials on the affected device.

  The vulnerability is due to incorrect mapping in the source code of task group assignments for a specific command. An attacker could exploit this vulnerability by issuing the command, which they should not be authorized to issue, on an affected device. A successful exploit could allow the attacker to invalidate the integrity of the disk and cause the device to restart. This vulnerability could allow a user with read permissions to issue a specific command that should require Administrator privileges.

  Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-cli-privescl-sDVEmhqv

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco IOS XR Software:

  • ASR 9000 Series Aggregation Services Routers (32-bit and 64-bit models)
  • IOS XR, SW only
  • Network Convergence System 1000 Series
  • Network Convergence System 5000 Series
  • Network Convergence System 5500 Series

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

  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:

  • 8000 Series Routers
  • Carrier Routing System
  • IOS XRv 9000 Routers
  • Network Convergence System 520 Routers
  • Network Convergence System 540 Series Routers
  • Network Convergence System 560 Series Routers
  • Network Convergence System 4000 Series 
  • Network Convergence System 4200 Series
  • Network Convergence System 6000 Series Routers

Workarounds

• Workarounds exist only for devices that have TACACS+ authentication, authorization, and accounting (AAA) command authorization configured. Administrators can use this feature to give nonadministrative users access to the commands that they require and deny access to all other commands.

  For more information about Cisco IOS XR task groups and AAA, see ASR9000/XR Using Task groups and understanding Priv levels and authorization.

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 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

  Cisco has fixed this vulnerability in Cisco IOS XR releases 7.1.2 and later for the following platforms:

  • ASR 9000 Series Aggregation Services Routers (32-bit and 64-bit models)
  • IOS XR, SW only
  • Network Convergence System 1000 Series
  • Network Convergence System 5000 Series
  • Network Convergence System 5500 Series

  Releases earlier than Release 7.0.1 are not vulnerable.

  The following software maintenance upgrades (SMUs) are also available. Customers should install the appropriate SMU as shown in the following table. Customers who require SMUs for other platforms and releases should contact their support organization.

  IOS XR Release	Platform	SMU Identifier
  7.0.2	ASR9K-X64	AA17739
  7.0.2	NCS5500	AA17740

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 Christopher York of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-cli-privescl-sDVEmhqv

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2020-SEP-02

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