Summary

• A vulnerability in the ingress packet processing path of Cisco Firepower Threat Defense (FTD) Software for interfaces that are configured either as Inline Pair or in Passive mode could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition.

  The vulnerability is due to insufficient validation when Ethernet frames are processed. An attacker could exploit this vulnerability by sending malicious Ethernet frames through an affected device. A successful exploit could allow the attacker do either of the following: 

  • Fill the /ngfw partition on the device: A full /ngfw partition could result in administrators being unable to log in to the device (including logging in through the console port) or the device being unable to boot up correctly. Note: Manual intervention is required to recover from this situation. Customers are advised to contact the Cisco Technical Assistance Center (TAC) to help recover a device in this condition.
  • Cause a process crash: The process crash would cause the device to reload. No manual intervention is necessary to recover the device after the reload.

  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:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-inline-dos-nXqUyEqM

  This advisory is part of the October 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication, which includes 17 Cisco Security Advisories that describe 17 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: October 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco products if they are running a vulnerable release of Cisco FTD Software with an interface that is configured in at least one of the following modes:

  • Inline Pair
  • Inline Pair with Tap
  • Passive
  • Passive (ERSPAN)

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

  Determine Whether Inline Pairs are Configured

  The checks in this section cover both Inline Pairs and Inline Pairs with Tap.

  Option 1: Use the CLI

  Use the show inline-set CLI command. If that command returns at least one Interface-Pair, the device is vulnerable. If the output is empty or the command does not exist, the device is not vulnerable. The following example shows the output of a device with an Inline Pair that has interfaces Ethernet1/6 and Ethernet1/8 configured:

  > show inline-set
  
  Inline-set Inline-Pair-1
    Mtu is 1500 bytes
    Failsafe mode is on/activated
    Failsecure mode is off
    Tap mode is off
    Propagate-link-state option is on
    hardware-bypass mode is disabled
    Interface-Pair[1]:
      Interface: Ethernet1/6 "INSIDE"
        Current-Status: UP
      Interface: Ethernet1/8 "OUTSIDE"
        Current-Status: UP
      Bridge Group ID: 509
  >

  Option 2: Use the Cisco Firepower Management Center (FMC) GUI

  Choose Devices > Device Management > [Edit Device] > Inline Sets and verify whether any Interface Pairs are configured.

  Note: Inline Sets cannot be configured using Cisco Firepower Device Manager (FDM).

  Determine Whether Passive Interfaces are Configured

  The checks in this section cover both Passive and Passive (ERSPAN) interfaces.

  Option 1: Use the CLI

  Access the Lina CLI by using the system support diagnostic-cli command. Then, use the show running-config interface | include mode passive command. If that command returns output, at least one passive interface is configured and the device is vulnerable. If that command returns empty output, the device is not vulnerable. The following example shows the output of the show running-config interface | include mode passive command on a device that has one passive interface configured:

  ftd# show running-config interface | include mode passive
   mode passive

  Option 2: Use the Cisco FMC GUI or FDM GUI

  In the Cisco FMC GUI, choose Devices > Device Management > [Edit Device] > Interfaces > [Edit Physical Interface] and verify whether any interfaces are set to Passive mode.

  In the Cisco FDM GUI, choose Device > Interfaces > [Edit Physical Interface] and verify whether any interfaces are set to Passive mode. If the Mode drop-down menu does not exist, passive interfaces cannot be configured on the platform and the device is not vulnerable.

  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 Appliance (ASA) Software
  • Firepower Management Center (FMC) Software

Workarounds

• There are no workarounds that address this vulnerability.

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.

  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 vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.

  Cisco FTD Software

  Cisco FTD Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Earlier than 6.2.21	Migrate to a fixed release.	Migrate to a fixed release.
  6.2.2	Migrate to a fixed release.	Migrate to a fixed release.
  6.2.3	Migrate to a fixed release.	Migrate to a fixed release.
  6.3.0	6.3.0.6 (future release)	Migrate to a fixed release.
  6.4.0	6.4.0.10	Migrate to a fixed release.
  6.5.0	6.5.0.5 (future release)	Migrate to a fixed release.
  6.6.0	6.6.1	6.6.1

  1. Cisco FMC and FTD Software releases 6.0.1 and earlier, as well as releases 6.2.0 and 6.2.1, have reached end of software maintenance. Customers are advised to migrate to a supported release that includes the fix for this vulnerability.

  To upgrade to a fixed release of Cisco FTD Software, do one of the following:

  • For devices that are managed by using Cisco Firepower Management Center (FMC), use the FMC interface to install the upgrade. After installation is complete, reapply the access control policy.
  • For devices that are managed by using Cisco Firepower Device Manager (FDM), use the FDM interface to install the upgrade. After installation is complete, reapply the access control policy.

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-ftd-inline-dos-nXqUyEqM

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2020-OCT-21

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