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             AUSCERT External Security Bulletin Redistribution

  Cisco Adaptive Security Appliance Software and Firepower Threat Defense
               Software Remote Code Execution Vulnerability
                              4 December 2019


        AusCERT Security Bulletin Summary

Product:           Cisco Adaptive Security Appliance (ASA)
                   Cisco Firepower Threat  Defense (FTD)
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Root Compromise -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-15992  

Original Bulletin: 

Revision History:  December  4 2019: Vendor added ASA fixed software release information
                   November 25 2019: Vendor added info on ASA fixes
                   November 20 2019: Updated fixed software release information
                                     and removed Cisco FTD Software Fixed Software table.
                   November 18 2019: Added fixed software release information.
                   November 14 2019: Initial Release

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Cisco Adaptive Security Appliance Software and Firepower Threat Defense
Software Remote Code Execution Vulnerability

Priority:        High
Advisory ID:     cisco-sa-20191112-asa-ftd-lua-rce
First Published: 2019 November 12 13:15 GMT
Last Updated:    2019 December 3 16:37 GMT
Version 2.3:     Interim

Workarounds:     No workarounds available

Cisco Bug IDs:   CSCvr85295CSCvr96680


CVSS Score:


  o A vulnerability in the implementation of the Lua interpreter integrated in
    Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat
    Defense (FTD) Software could allow an authenticated, remote attacker to
    execute arbitrary code with root privileges on the underlying Linux
    operating system of an affected device.

    The vulnerability is due to insufficient restrictions on the allowed Lua
    function calls within the context of user-supplied Lua scripts. A
    successful exploit could allow the attacker to trigger a heap overflow
    condition and execute arbitrary code with root privileges on the underlying
    Linux operating system of an affected device.

    Update November 19, 2019: Advisory version 1.1 contained a Fixed Software
    table advising that Vulnerability Database (VDB) Update 329 contained a fix
    for this vulnerability for Cisco FTD Software. It has been discovered since
    release of VDB Update 329 that this fix does not provide adequate
    mitigation for this vulnerability. Customers are advised to wait for an
    update to this advisory and for a new fix to be posted.

    Cisco has released software updates that address this vulnerability for
    Cisco ASA Software and will release additional software updates that will
    address this vulnerability for ASA Software and for FTD Software. There are
    no workarounds that address this vulnerability.

    This advisory is available at the following link:

Affected Products

  o Vulnerable Products

    This vulnerability affects all versions of Cisco ASA Software and Cisco FTD

    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:

       Adaptive Security Device Manager
       Cisco Security Manager
       Firepower Management Center
       Firepower Management Center 1000


  o At publication time, the vulnerability described in this advisory had been
    identified in the following Cisco Products:

    Cisco Adaptive Security Appliance (ASA) Software

    The Dynamic Access Policy (DAP) feature of Cisco ASA Software allows an
    administrator to create policies that apply the appropriate access control
    attributes based on factors dynamically assessed at the time of the
    establishment of the VPN session. DAP offers the capability of defining
    enhanced authentication, authorization, and accounting (AAA) policies by
    using the Lua programming language. These user-defined Lua scripts are
    executed within the scripting sandbox of the device.

    The local implementation of the Lua interpreter, however, imposes
    insufficient restrictions on the allowed Lua function calls within the
    scripting sandbox of the affected device. An attacker who has valid
    administrative credentials can submit a malicious Lua script that, on
    execution, will escape the scripting sandbox and execute arbitrary code
    with root privileges on the underlying Linux Operating System of an
    affected device.

    Cisco Firepower Threat Defense (FTD) Software

    The Custom Application Detectors feature allows an administrator to define
    custom logic to identify and filter IP traffic based on user-defined
    applications on Cisco FTD devices managed through Firepower Management
    Center (FMC).

    As part of the process of defining custom application detection logic, an
    administrator can create two types of detectors: Basic or Advanced. Basic
    application detectors are created in the FMC web-based interface by filling
    out a series of web form fields. Advanced application detectors are created
    externally and uploaded to the FMC web interface as custom Lua files that
    contain user-defined application detector logic. Once configured, the
    advanced custom application detectors are downloaded and executed within
    the scripting sandbox of the managed FTD device.

    An attacker who has valid administrative credentials can configure an
    Advanced Detector on the FMC web interface and submit a malicious Lua
    script. The detector configuration and the malicious script will be pushed
    to a managed FTD device. On execution, the malicious script will escape the
    scripting sandbox and execute arbitrary code with root privileges on the
    underlying Linux operating system of the FTD device.


  o There are no workarounds that address this vulnerability.

Fixed Software

  o Cisco has released free updates for Cisco ASA Software that address the
    vulnerability described in this advisory. Cisco will release additional
    free updates for ASA Software and free updates for FTD Software that will
    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

    Cisco ASA Software

    In the following table, the left column lists major releases of Cisco ASA
    Software. The right column indicates the first release that includes the
    fix for this vulnerability.

    If a future release date is indicated for software, the date provided
    represents an estimate based on all information known to Cisco as of the
    Last Updated date at the top of the advisory. Availability dates are
    subject to change based on a number of factors, including satisfactory
    testing results and delivery of other priority features and fixes. If no
    version or date is listed for an affected software release (indicated by a
    blank field and/or an advisory designation of Interim), Cisco is continuing
    to evaluate the fix and will update the advisory as additional information
    becomes available. After the advisory is marked Final, customers should
    refer to Cisco bug CSCvr85295 for further details.

    Cisco ASA Software Release   First Fixed Release for This Vulnerability
    Prior to 9.4 ^1     (Available)
    9.4 ^1              (Available)
    9.5 ^1              (Available)
    9.6                 (Available)
    9.7 ^1                       Migrate to
    9.8                 (Available)
    9.9                 (December 2019)
    9.10                (December 2019)
    9.12                         9.12.3 (Available)
    9.13                (January 2020)

    1. Cisco ASA Software releases 9.4 and earlier and Cisco ASA Software
    releases 9.5 and 9.7 have reached end of maintenance. Customers should
    migrate to a supported release that includes the fix for this

    Cisco FTD Software

    Cisco will release software updates that will address this vulnerability
    for Cisco FTD Software.

Exploitation and Public Announcements

  o The Cisco Product Security Incident Response Team (PSIRT) is aware that
    proof-of-concept exploit code is available for the vulnerability described
    in this advisory.

    Cisco PSIRT is not aware of any malicious use of the vulnerability that is
    described in this advisory.


  o Cisco would like to thank md4 of HatLab@DBAPPSecurity for reporting this

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       |
    |         | Added ASA fixed       | Fixed    |         |                  |
    | 2.3     | software release      | Software | Interim | 2019-December-03 |
    |         | information.          |          |         |                  |
    |         | Fixed formatting and  |          |         |                  |
    | 2.2     | typo in ASA fixed     | Fixed    | Interim | 2019-November-27 |
    |         | software release      | Software |         |                  |
    |         | information.          |          |         |                  |
    |         | Added ASA fixed       | Summary  |         |                  |
    | 2.1     | software release      | and      | Interim | 2019-November-22 |
    |         | information.          | Fixed    |         |                  |
    |         |                       | Software |         |                  |
    |         | Updated fixed         |          |         |                  |
    |         | software release      | Summary  |         |                  |
    | 2.0     | information and       | and      | Interim | 2019-November-19 |
    |         | removed Cisco FTD     | Fixed    |         |                  |
    |         | Software Fixed        | Software |         |                  |
    |         | Software table.       |          |         |                  |
    |         | Added fixed software  | Summary  |         |                  |
    |         | release information   | and      |         |                  |
    | 1.1     | to the Summary and    | Fixed    | Interim | 2019-November-15 |
    |         | Fixed Software        | Software |         |                  |
    |         | sections.             |          |         |                  |
    | 1.0     | Initial public        | -        | Interim | 2019-November-12 |
    |         | release.              |          |         |                  |

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