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             AUSCERT External Security Bulletin Redistribution

         Cisco IOS Access Points Software 802.11r Fast Transition
                      Denial of Service Vulnerability
                               18 July 2019


        AusCERT Security Bulletin Summary

Product:           Cisco IOS Access Points
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-1920  

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco IOS Access Points Software 802.11r Fast Transition Denial of Service

Priority:        High

Advisory ID:     cisco-sa-20190717-aironet-dos

First Published: 2019 July 17 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds availableCisco Bug IDs:   CSCvg95745



CVSS Score:


  o A vulnerability in the 802.11r Fast Transition (FT) implementation for
    Cisco IOS Access Points (APs) Software could allow an unauthenticated,
    adjacent attacker to cause a denial of service (DoS) condition on an
    affected interface.

    The vulnerability is due to a lack of complete error handling condition for
    client authentication requests sent to a targeted interface configured for
    FT. An attacker could exploit this vulnerability by sending crafted
    authentication request traffic to the targeted interface, causing the
    device to restart unexpectedly.

    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:

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco Access Points that are running an affected
    version of Cisco IOS Access Point Software configured for 802.11r FT.

    Verification of 802.11r Fast Transition (FT) Configuration From the CLI:


    From the CLI of the WLC for which the AP is associated, administrators may
    issue the following show command to verify if the 802.11r FT feature is
    configured on the device.


        (Cisco Controller) > show wlan <wlan id>



        802.11 Authentication................Open System

        FT Support.....................Disabled

        Static WEP Keys................Disabled


        Wi-Fi Protected Access (WPA/WPA2).....Enabled

    Verifying 802.11r Fast Transition (FT) Configuration From the (GUI) :


    Step 1 : Choose the WLANs tab to open the WLANs window.
    Step 2 : Click a WLAN ID .
    Step 3 : Choose Security > Layer 2 to verify if the Fast Transition feature
    is enabled or disabled on the device.

    It is important to note the available adaptive option that exists within
    the drop-down menu when configuring 802.11r Fast Transition for the
    respective WLAN. This feature, if selected, could allow compatible 802.11r
    Fast Transition wireless clients to utilize Fast Transition and become
    vulnerable to the issue listed in the Summary section.

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

    Products Confirmed Not Vulnerable

    No other Cisco products are known to be affected by this vulnerability.


  o There are no workarounds that address this vulnerability.

Fixed Software

  o 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:

    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 and Alerts 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

    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:

    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

    Fixed Releases

    In the following table, the left column lists major Cisco software
    releases. The right column indicates whether a major release is affected by
    the vulnerability described in this advisory and the first minor release
    that includes the fix for this vulnerability.

    Cisco IOS Access Points Major Software  First Fixed Release for This
    Release                                 Vulnerability
    Prior to 8.0                  
    8.8                                     Not vulnerable
    8.9                                     Not vulnerable

Exploitation and Public Announcements

  o 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.


  o This vulnerability was found during the resolution of a Cisco TAC support

Cisco Security Vulnerability Policy

  o To learn about Cisco security vulnerability disclosure policies and
    publications, see the Security Vulnerability Policy . This document also
    contains instructions for obtaining fixed software and receiving security
    vulnerability information from Cisco.


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/

Revision History

  o +---------+---------------------------+---------+--------+---------------+
    | Version |        Description        | Section | Status |     Date      |
    | 1.0     | Initial public release.   | -       | Final  | 2019-July-17  |

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