Summary

• Multiple vulnerabilities in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition.

  These vulnerabilities are due to improper input validation when parsing HTTPS requests. An attacker could exploit these vulnerabilities by sending a malicious HTTPS request to 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 these vulnerabilities. There are no workarounds that address these vulnerabilities.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asafdt-webvpn-dos-KSqJAKPA

  This advisory is part of the October 2021 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: October 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  These vulnerabilities affect Cisco products if they are running a vulnerable release of Cisco ASA Software or Cisco FTD Software with a vulnerable AnyConnect or WebVPN configuration.

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

  Determine the ASA Software Configuration

  Use the show-running-config CLI command to determine whether the software has a vulnerable feature configured. In the following table, the left column lists the Cisco ASA Software features that are vulnerable. The right column indicates the basic configuration for each feature from the show running-config CLI command. If a device is running a vulnerable release and has one of these features configured, it is vulnerable.

  Cisco ASA Feature	Vulnerable Configuration
  AnyConnect Internet Key Exchange Version 2 Remote Access (with client services)	crypto ikev2 enable <interface_name> client-services port <port #>
  AnyConnect SSL VPN	webvpn enable <interface_name>
  Clientless SSL VPN	webvpn enable <interface_name>

  Determine the FTD Software Configuration

  Use the show-running-config CLI command to determine whether the software has a vulnerable feature configured. In the following table, the left column lists the Cisco FTD Software features that are vulnerable. The right column indicates the basic configuration for each feature from the show running-config CLI command. If a device is running a vulnerable release and has one of these features configured, it is vulnerable.

  Cisco FTD Feature	Vulnerable Configuration
  AnyConnect Internet Key Exchange Version 2 Remote Access (with client services)1,2	crypto ikev2 enable <interface_name> client-services port <port #>
  AnyConnect SSL VPN1,2	webvpn enable <interface_name>

  1. Remote Access VPN features were introduced in Cisco FTD Software Release 6.2.2.

  2. Remote Access VPN features are enabled by using Devices > VPN > Remote Access in Cisco Firepower Management Center (FMC) or by using Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).

  Products Confirmed Not Vulnerable

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

  Cisco has confirmed that these vulnerabilities do not affect Cisco Firepower Management Center (FMC) Software.

Workarounds

• There are no workarounds that address these vulnerabilities.

Fixed Software

• Cisco has released free software updates that address the vulnerabilities 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 columns indicate whether a release is affected by the vulnerabilities described in this advisory and the first release that includes the fix for these vulnerabilities. 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 vulnerabilities.

  ASA Software

  Cisco ASA Major Release	First Fixed Release for CVE-2021-1573	First Fixed Release for CVE-2021-34704	First Fixed Release for CVE-2021-40118	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  9.7 and earlier1	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  9.8	9.8.4.40	Not vulnerable.	9.8.4.40	9.8.4.40
  9.91	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  9.101	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  9.12	9.12.4.26	Not vulnerable.	9.12.4.29	9.12.4.29
  9.131	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  9.14	9.14.3	Not vulnerable.	9.14.3.9	9.14.3.9
  9.15	9.15.1.17	9.15.1.17	9.15.1.17	9.15.1.17
  9.16	9.16.1.28	9.16.2	9.16.2.3	9.16.2.3

  1. Cisco ASA Software releases 9.7 and earlier as well as releases 9.9, 9.10, and 9.13 have reached end of software maintenance. Customers are advised to migrate to a supported release that includes the fix for these vulnerabilities.

  FTD Software

  Cisco FTD Major Release	First Fixed Release for CVE-2021-1573	First Fixed Release for CVE-2021-34704	First Fixed Release for CVE-2021-40118	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  6.2.2 and earlier1	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  6.2.3	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  6.3.01	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  6.4.0	6.4.0.13 (Nov 2021)	Not vulnerable.	6.4.0.13 (Nov 2021)	6.4.0.13 (Nov 2021)
  6.5.01	Migrate to a fixed release.	Not vulnerable.	Migrate to a fixed release.	Migrate to a fixed release.
  6.6.0	6.6.5	Not vulnerable.	6.6.5	6.6.5.1 (Nov 2021)
  6.7.0	6.7.0.3 (Jan 2022)	6.7.0.3 (Jan 2022)	6.7.0.3 (Jan 2022)	6.7.0.3 (Jan 2022)
  7.0.0	7.0.1	7.0.1	7.0.1	7.0.1

  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 these vulnerabilities.

  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 advisory.

Exploitation and Public Announcements

• The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Source

• CVE-2021-1573 was found during internal security testing.

  Cisco would like to thank Nikita Abramov of Positive Technologies for reporting CVE-2021-34704.

  Cisco would like to thank Ruslan Sayfiev, Denis Faiustov, and Masahiro Kawada of Ierae Security for reporting CVE-2021-40118.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asafdt-webvpn-dos-KSqJAKPA

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2021-OCT-27

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