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             AUSCERT External Security Bulletin Redistribution

        Cisco Firepower Threat Defense Software TCP Proxy Denial of
                           Service Vulnerability
                               29 April 2022


        AusCERT Security Bulletin Summary

Product:           Cisco Firepower Threat Defense Software
Publisher:         Cisco Systems
Operating System:  Cisco
Resolution:        Patch/Upgrade
CVE Names:         CVE-2022-20746  

Original Bulletin: 

Comment: CVSS (Max):  8.6 CVE-2022-20746 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
         CVSS Source: Cisco Systems
         Calculator:  https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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Cisco Firepower Threat Defense Software TCP Proxy Denial of Service

Priority:        High
Advisory ID:     cisco-sa-ftd-tcp-dos-kM9SHhOu
First Published: 2022 April 27 16:00 GMT
Version 1.0:     Final
Workarounds:     No workarounds available
Cisco Bug IDs:   CSCvz00032
CVE Names:       CVE-2022-20746
CWEs:            CWE-476


  o A vulnerability in the TCP proxy functionality of Cisco Firepower Threat
    Defense (FTD) Software could allow an unauthenticated, remote attacker to
    trigger a denial of service (DoS) condition.

    This vulnerability is due to improper handling of TCP flows. An attacker
    could exploit this vulnerability by sending a crafted stream of TCP traffic
    through an affected device. A successful exploit could allow the attacker
    to cause the 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.

    This advisory is available at the following link:

    This advisory is part of the April 2022 release of the Cisco ASA, FTD, and
    FMC Security Advisory Bundled publication. For a complete list of the
    advisories and links to them, see Cisco Event Response: April 2022 Cisco
    ASA, FMC, and FTD Software Security Advisory Bundled Publication .

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco products if they are running Cisco FTD
    Software Release 7.0.0 or Release and have the TCP Intercept
    feature enabled.

    Determine the TCP Intercept Configuration

    To determine the status of the TCP Intercept feature, use the show
    running-config policy-map | include embryonic command on the device CLI. If
    the command returns output, TCP Intercept is enabled and the device is
    affected by this vulnerability. If the command does not return output, TCP
    Intercept is disabled and the device is not affected by this vulnerability.

    The following example shows the output of a device on which TCP Intercept
    is enabled with both a global limit and a per-client limit of one for
    half-open (embryonic) TCP connections:

        ftd# show running-config policy-map | include embryonic
          set connection embryonic-conn-max 1 per-client-embryonic-max 1

    Having either a global ( embryonic-conn-max) or a per client ( 
    per-client-embryonic-max ) limit configured is sufficient to enable the TCP
    Intercept feature. The exact value of these limits does not affect the
    vulnerability status of the device.

    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 Cisco Adaptive
    Security Appliance (ASA) Software or Cisco Firepower Management Center
    (FMC) Software.


  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 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:

    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

    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

    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(s), the left column lists Cisco software releases.
    The center column indicates whether a release is affected by the
    vulnerability described in this advisory and the first release that
    includes the fix for this vulnerability. The right column indicates whether
    a release is affected by any of the Critical or High SIR vulnerabilities
    described in this bundle and which release includes fixes for those

    FTD Software

    Cisco FTD     First Fixed Release  First Fixed Release for All
    Software      for This             Vulnerabilities Described in the Bundle
    Release       Vulnerability        of Advisories
    6.2.2 and     Not vulnerable.      Migrate to a fixed release.
    earlier ^1
    6.2.3         Not vulnerable.      Migrate to a fixed release.
    6.3.0 ^1      Not vulnerable.      Migrate to a fixed release.
    6.4.0         Not vulnerable. (May 2022)
    6.5.0 ^1      Not vulnerable.      Migrate to a fixed release.
    6.6.0         Not vulnerable.
    6.7.0         Not vulnerable.      Migrate to a fixed release.
    7.0.0         7.0.1                7.0.2 (May 2022)
    7.1.0         Not vulnerable.

    1. Cisco FMC and FTD Software releases 6.2.2 and earlier, as well as
    releases 6.3.0 and 6.5.0, have reached end of software maintenance .
    Customers are advised to migrate to a supported release that includes the
    fix for this vulnerability.

    For instructions on upgrading your FTD device, see Cisco Firepower
    Management Center Upgrade Guide .

    The Cisco Product Security Incident Response Team (PSIRT) validates only
    the affected and fixed release information that is documented in this

Exploitation and Public Announcements

  o The Cisco 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.

Related to This Advisory

  o Cisco Event Response: April 2022 Cisco ASA, FMC, and FTD Software Security
    Advisory Bundled Publication


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tcp-dos-kM9SHhOu

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2022-APR-27  |

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