Summary

• A vulnerability in the WPA2 and WPA3 security implementation of Cisco IOS XE Wireless Controller Software for the Cisco Catalyst 9000 Family could allow an unauthenticated, adjacent attacker to cause denial of service (DoS) condition on an affected device.

  The vulnerability is due to incorrect packet processing during the WPA2 and WPA3 authentication handshake when configured for dot1x or pre-shared key (PSK) authentication key management (AKM) with 802.11r BSS Fast Transition (FT) enabled. An attacker could exploit this vulnerability by sending a crafted authentication packet to an affected device. A successful exploit could cause an affected device to reload, resulting in a DoS condition.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  Note: Valid credentials for dot1x or PSK AKM to access the WLAN are required to exploit this vulnerability

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-wpa-dos-cXshjerc

  This advisory is part of the September 24, 2020, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 25 Cisco Security Advisories that describe 34 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: September 2020 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco IOS XE Wireless Controller Software for the Cisco Catalyst 9000 Family if a device is running a vulnerable software release with dot1x or PSK AKM configured and has the FT feature enabled within a WLAN. The following hardware platforms are vulnerable:

  • Catalyst 9800 Embedded Wireless Controller for Catalyst 9300, 9400, and 9500 Series Switches
  • Catalyst 9800 Series Wireless Controllers

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

  Determine the Device Configuration

  To determine if a device has a vulnerable configuration, log in to the device and execute the show running-config all CLI command. Some configuration elements are default and will not be displayed without the all parameter.
  

  For a vulnerable AKM configuration, verify if any of the following elements are configured:

  • A WLAN using dot1x AKM will have security wpa akm dot1x or security wpa akm ft dot1x configured.
  • A WLAN using PSK AKM will have security wpa akm psk or security wpa akm ft psk configured.

  To verify if FT is enabled within a WLAN configured with a vulnerable AKM, confirm if either element listed below is present:

  • security ft
  • security ft adaptive

  Vulnerable configuration examples are as follows:

  Dot1x

  Dot1x with Adaptive 11r WLAN:
  wlan dot1x 1 dot1x
   security ft adaptive
   security wpa akm dot1x
   security dot1x authentication-list eap_methods
   no shutdown
   
  11r-dot1x WLAN:
  wlan 11r-dot1x 2 11r-dot1x
   security ft
   security wpa akm ft dot1x
   security dot1x authentication-list eap_methods
   no shutdown
  

  PSK

  PSK with Adaptive 11r WLAN:
  wlan psk 3 psk
   security ft adaptive
   security wpa psk set-key ascii 0 cisco123
   no security wpa akm dot1x
   security wpa akm psk
   no shutdown
   
  11r-PSK WLAN:
  wlan 11r-psk 4 11r-psk
   security ft
   security wpa psk set-key ascii 0 cisco123
   no security wpa akm dot1x
   security wpa akm ft psk
   no shutdown

  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:

  • Embedded Wireless Controller on Catalyst 9100 Access Points
  • IOS Software
  • IOS XR Software
  • NX-OS Software
  • WLC Software

Workarounds

• There are no workarounds that address this vulnerability.

  However, customers can disable the 802.11r Fast Transition (FT) feature as a mitigation. Executing the no security ft or no security ft adaptive command will disable this feature and prevent this exploit. The following examples are for dot1x.

  Note: Before making this configuration change, ensure that the WLAN is in a shutdown state.

  
  11r-dot1x WLAN:
  wlan 11r-dot1x 2 11r-dot1x
   no security ft
   security wpa akm ft dot1x
   security dot1x authentication-list eap_methods
   no shutdown
   
  Dot1x with Adaptive 11r WLAN:
  wlan dot1x 1 dot1x
   no security ft adaptive
   security wpa akm dot1x
   security dot1x authentication-list eap_methods
   no shutdown
  

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.

  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-wpa-dos-cXshjerc

Revision History

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

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