Summary

• A vulnerability in the Authentication, Authorization, and Accounting (AAA) feature of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to bypass command authorization and copy files to or from the file system of an affected device using the Secure Copy Protocol (SCP).

  This vulnerability is due to incorrect processing of SCP commands in AAA command authorization checks. An attacker with valid credentials and level 15 privileges could exploit this vulnerability by using SCP to connect to an affected device from an external machine. A successful exploit could allow the attacker to obtain or change the configuration of the affected device and put files on or retrieve files from the affected device.

  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-aaascp-Tyj4fEJm

  This advisory is part of the September 2023 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2023 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco products if they are running a vulnerable release of Cisco IOS Software or Cisco IOS XE Software (in either autonomous mode or controller mode) and have both SCP server functionality and AAA command authorization enabled. However, whether the device is exploitable is dependent on how the TACACS+ profiles for each user are configured. For more information, see the Details section of this advisory.

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

  Determine the SCP Server Configuration

  To determine whether a device is configured to enable the SCP server, log in to the device and use the show running-config | include ip scp server enable command in the CLI. If the device is configured to enable the SCP server, the output will include the ip scp server enable command, as shown in the following example:

  Router# show running-config | include ip scp server enable
  ip scp server enable
  Router#

  If the show running-config | include ip scp server enable command does not return any output, the device is not configured to enable the SCP server.

  Determine the AAA Configuration

  To determine whether a device is configured to use AAA for command authorization, log in to the device and use the show running-config | include aaa authorization commands command in the CLI. If the command returns any output, the device is configured to use AAA command authorization, as shown in the following example:

  Router# show running-config | include aaa authorization commands
  aaa authorization commands 15 ISE_aaa group ISESERVER local
  Router#

   

  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 XR Software
  • Meraki products
  • NX-OS Software

Details

• When the SCP server is enabled, a user who has appropriate authorization can copy any file to or from the Cisco IOS file system, including images and configurations. Only users who are assigned privilege level 15 are allowed to use the SCP server. Administrators may further restrict what actions an authenticated user may do by enforcing command authorization. Command authorization is enforced by privilege level.

  The impact to a customer from this vulnerability is dependent on how their policies for privilege level 15 users are defined. In a scenario where the device has restrictions on privilege level 15 users that prevent them from viewing or changing the configuration, a user could change the configuration by obtaining the configuration through SCP, making changes to the configuration locally, and then copying the configuration back to the device using SCP.

  If AAA command authorization is enabled, the SCP command should be processed by the configuration line aaa authorization commands 15, given that the SCP user must be a privilege level 15 user. However, due to this vulnerability, the request is handled by the configuration line aaa authorization commands 0 instead.

  SCP client functionality is not affected.

  SSH server and client functionality is not affected.

Workarounds

• There is a workaround and a mitigation that address this vulnerability.

  As a workaround for this vulnerability, enable privilege level 0 command authorization checks. To force the AAA server to check SCP server commands, use the configuration command aaa authorization commands 0 and configure the appropriate command policy to prevent a user from using SCP server commands. To allow or deny file uploads or downloads through SCP, add filters to the AAA configuration for the commands scp -f and scp -t.

  As a mitigation for this vulnerability, disable the SCP server functionality using the configuration command no ip scp server enable. Administrators could then use the SCP client functionality on the affected device to copy images or configurations to or from the router.

  While this workaround and this mitigation have been deployed and were proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

• Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.

  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.

  The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.

  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.

  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. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”). 

  To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to determine whether a release is affected by any Cisco Security Advisory. To use the form, follow these steps:

  1. Choose which advisories the tool will search—only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
  2. Enter a release number—for example, 15.9(3)M2 or 17.3.3.
  3. Click Check.

   

  Only this advisory All Critical and High advisories All advisories

   

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 Hendrik Van Belleghem for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aaascp-Tyj4fEJm

Revision History

• Version	Description	Section	Status	Date
  1.1	Added attribution.	Source	Final	2023-OCT-13
  1.0	Initial public release.	—	Final	2023-SEP-27

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