Summary

• A vulnerability in the data acquisition (DAQ) component of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured access control policies or cause a denial of service (DoS) condition.

  The vulnerability exists because the affected software improperly manages system memory resources when inspecting traffic. An attacker could exploit this vulnerability by generating specific traffic patterns for the software to inspect. A successful exploit could allow the attacker to exhaust system memory resources used for traffic inspection. Depending on the configuration, the FTD Software could fail open and cease to inspect traffic or fail closed and result in a DoS condition. This vulnerability may require manual intervention to restore the software.

  Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190123-firepowertds-bypass

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Firepower Threat Defense Software Release 6.3.0 only when running on Firepower 4100 or Firepower 9300 Series Platforms.

  Determine a Vulnerable FTD Software Configuration

  To verify whether the FTD Software has a vulnerable configuration, administrators can check access control policies and general configurations. To be considered vulnerable, the configuration must have all of the following:

  1. Access control rules that perform URL filtering or invoke file/malware inspection
  2. SSL hardware acceleration enabled (default setting)
  3. Access control policy advanced settings that do not specify an associated SSL policy to handle encrypted traffic (default setting)

  Note: If the Snort Fail Open: Busy option under Inline Sets > Advanced is enabled, exploit attempts can cause traffic to pass through without inspection when the Snort process is busy. If the Busy option is not enabled, exploit attempts can cause a DoS condition.

  Determine the Cisco Firepower System Software Release

  To determine which Cisco Firepower System Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco Firepower System Software Release 6.3.0:

  > show version 
  -------[ ftd.domain.com ]--------
  Model : Cisco Firepower 4140 Threat Defense (76) Version 6.3.0 (Build 83)
  UUID : 06870e8a-15a7-11e9-b733-a3ffca9e3696
  Rules update version : 2019-01-14-001-vrt
  VDB version : 299
  ----------------------------------------------------
  
  

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

Indicators of Compromise

• Exploitation of this vulnerability can lead to a decrease in available system memory. Administrators can issue the show blocks command; an available block count in the CNT column that shows a continued decrease in the memory blocks of size 9344 could indicate active exploitation.

  # show blocks
    SIZE    MAX    LOW    CNT
       0   2700   2693   2700
       4    100     99     99
      80   1196   1135   1196
     256   4148   3953   4124
    1550   6494   6405   6489
    2048    100    100    100
    2560    164    164    164
    4096    100    100    100
    8192    100    100    100
    9344  48552    516    535
   16384    100    100    100
   65536     16     16     16

  A depletion of the memory blocks of size 9344 could cause traffic inspection to cease and may prevent network policies from being applied. If these conditions are observed, customers are advised to contact the Cisco Technical Assistance Center (TAC) to determine whether the device has been compromised by exploitation of this vulnerability.

Workarounds

• Disabling SSL hardware acceleration, which is enabled by default in FTD Software Release 6.3.0, mitigates this vulnerability when no SSL policy is applied. Configurations with SSL policies enabled are not vulnerable.

  Administrators can issue the system support ssl-hw-offload disable command in the CLI to disable SSL hardware acceleration. This command will reboot the device.

  ftd# system support ssl-hw-offload disable

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 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 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, the left column lists releases of Cisco Firepower System Software. The right 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.

  Cisco Firepower System Software Release	First Fixed Release
  6.1.0	Not vulnerable
  6.2.0	Not vulnerable
  6.2.1	Not vulnerable
  6.2.2	Not vulnerable
  6.2.3	Not vulnerable
  6.3.01	Affected; apply 6.3.0 Hotfix B

  ¹6.3.0 Build 85 or later is not vulnerable.
  

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-20190123-firepowertds-bypass

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2019-January-23

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