Summary

• A vulnerability in the software-based SSL/TLS message handler of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition.

  The vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message through an affected device. SSL/TLS messages sent to an affected device do not trigger this vulnerability. A successful exploit could allow the attacker to cause a process to crash. This crash would then trigger a reload of the device. No manual intervention is needed 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-ssl-decrypt-dos-DdyLuK6c

  This advisory is part of the April 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: April 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco FTD Software, have an SSL decryption policy enabled, and are running one of the following hardware platforms:

  • 3000 Series Industrial Security Appliances (ISAs)
  • ASA 5512-X Adaptive Security Appliance
  • ASA 5515-X Adaptive Security Appliance
  • ASA 5525-X Adaptive Security Appliance
  • ASA 5545-X Adaptive Security Appliance
  • ASA 5555-X Adaptive Security Appliance
  • Firepower 1000 Series
  • Firepower 2100 Series
  • Firepower Threat Defense Virtual (FTDv)

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

  Determine Whether an SSL Decryption Policy Is Enabled

  There are two methods for determining whether an SSL decryption policy is enabled:

  Option 1: Use the CLI

  Use the show ssl-policy-config CLI command to verify whether an SSL decryption policy is enabled on a device. The following example shows the output of the show ssl-policy-config command on a device that does not have an SSL policy configured and is not vulnerable:

  > show ssl-policy-config
  SSL policy not yet applied.

  Any other output returned by the show ssl-policy-config command indicates that an SSL policy is configured and the device is vulnerable.

  For more information about the show ssl-policy-config command, see the Cisco Firepower Threat Defense Command Reference.

  Option 2: Use the GUI

  To determine whether an SSL decryption policy is enabled on a device, check the appropriate policy:

  • For devices managed by Firepower Management Center (FMC):
    Policies > Access Control > SSL
  • For devices managed by Firepower Device Manager (FDM):
    Policies > SSL Decryption

   

  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
  • FTD Software that is running on any platform other than the platforms listed in the Vulnerable Products section of this advisory

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.

  FTD Software

  Cisco FTD Software Release	First Fixed Release for This Vulnerability	Recommended Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  Earlier than 6.2.21	Not vulnerable.	Migrate to a fixed release.
  6.2.2	Not vulnerable.	Migrate to a fixed release.
  6.2.3	Not vulnerable.	Migrate to a fixed release.
  6.3.0	Migrate to a fixed release.	Migrate to a fixed release.
  6.4.0	Not vulnerable.	6.4.0.12 (May 2021)
  6.5.0	Not vulnerable.	Migrate to a fixed release.
  6.6.0	Not vulnerable.	6.6.42
  6.7.0	Not vulnerable.	6.7.0.2

  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.

  2. The First Fixed Release for the 6.6.0 code train was 6.6.3; however, due to upgrade issues associated with CSCvx86231 the recommended release is 6.6.4.

  To upgrade to a fixed release of Cisco FTD Software, customers can 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 by Sanmith Prakash of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-ssl-decrypt-dos-DdyLuK6c

Revision History

• Version	Description	Section	Status	Date
  1.1	Updated the Fixed Releases table to more clearly identify releases that are not vulnerable.	Fixed Software	Final	2021-JUN-08
  1.0	Initial public release.	—	Final	2021-APR-28

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