Summary

• A vulnerability in an IPsec VPN library of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to read or modify data within an IPsec IKEv2 VPN tunnel.

  This vulnerability is due to an improper implementation of Galois/Counter Mode (GCM) ciphers. An attacker in a man-in-the-middle position could exploit this vulnerability by intercepting a sufficient number of encrypted messages across an affected IPsec IKEv2 VPN tunnel and then using cryptanalytic techniques to break the encryption. A successful exploit could allow the attacker to decrypt, read, modify, and re-encrypt data that is transmitted across an affected IPsec IKEv2 VPN tunnel.

  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-asaftd-ipsec-mitm-CKnLr4

  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

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco ASA Software or Cisco FTD Software and have an IPsec IKEv2 VPN (either Remote Access or LAN-to-LAN) using a GCM cipher configured:

  • Firepower 4112, 4115, 4125, and 4145 Appliances
  • Firepower 9300 Security Appliances with SM-40, SM-48, or SM-56

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

  Determine the IPsec IKEv2 VPN Configuration

  To assess the IPsec IKEv2 VPN configuration, confirm that both of the following are true:

  • IKEv2 is enabled on at least one interface
  • At least one configured IPsec IKEv2 proposal uses a GCM cipher

  To determine whether IKEv2 is enabled on an interface, use the show running-config crypto ikev2 | include enable CLI command. If that command returns output, IKEv2 is enabled on at least one interface. The following example shows the output of the show running-config crypto ikev2 | include enable command on a device that has IKEv2 enabled on the outside interface:

  firewall# show running-config crypto ikev2 | include enable
  crypto ikev2 enable outside client-services port 443

  To determine whether at least one IPsec IKEv2 proposal is configured to use a GCM cipher, use the show running-config crypto ipsec | include gcm CLI command. If that command returns output, at least one configured IPsec IKEv2 proposal uses a GCM cipher. The following example shows the output of the show running-config crypto ipsec | include gcm command on a device that uses the AES-GCM cipher in an IPsec IKEv2 proposal:

  firewall# show running-config crypto ipsec | include gcm
   protocol esp encryption aes-gcm

  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:

  • 3000 Series Industrial Security Appliances (ISAs)
  • Adaptive Security Virtual Appliances (ASAv)
  • ASA 5505 Series Adaptive Security Appliances
  • ASA 5500-X Series Firewalls
  • ASA Services Modules for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
  • Firepower 1000 Series
  • Firepower 2100 Series
  • Firepower 4110, 4120, 4140, and 4150 Appliances
  • Firepower 9300 Series Security Appliance with SM-24, SM-36, or SM-44
  • Firepower Management Center (FMC) Software
  • Firepower Threat Defense Virtual (FTDv)
  • Next-Generation Intrusion Prevention System (NGIPS) Software

Workarounds

• There is a workaround that addresses this vulnerability. To remove the attack vector for this vulnerability, reconfigure all existing IPsec IKEv2 proposals to use a non-GCM cipher.

  For example, if you have the following IPsec IKEv2 proposal configured:

  firewall# show running-config crypto ipsec 
  crypto ipsec ikev2 ipsec-proposal AES-GCM
   protocol esp encryption aes-gcm
   protocol esp integrity null

  Reconfigure that as follows:

  firewall# configure terminal 
  firewall(config)# crypto ipsec ikev2 ipsec-proposal AES-GCM
  firewall(config-ipsec-proposal)# protocol esp integrity sha-256 
  WARNING: GCM\GMAC are authenticated encryption algorithms.esp integrity config is ignored
  firewall(config-ipsec-proposal)# protocol esp encryption aes-256    
  firewall# show running-config crypto ipsec 
  crypto ipsec ikev2 ipsec-proposal AES-GCM
   protocol esp encryption aes-256
   protocol esp integrity sha-256

  Note: GCM ciphers are inherently authenticated, thus the configured integrity algorithm is ignored for these ciphers and the null cipher is recommended. When changing to a non-GCM cipher, first configure a valid integrity algorithm as well.

  For all available options, see Cisco ASA Series Command Reference.

  For LAN-to-LAN IPsec IKEv2 VPN connections, match the configuration on the remote side accordingly to ensure that the VPN tunnels keep working.

  To completely close the attack vector, force all existing IPsec IKEv2 VPN connections to log off and then re-establish their session using the new ciphers as follows:

  firewall# vpn-sessiondb logoff protocol ikev2 
  Do you want to logoff the VPN session(s)? [confirm] 
  INFO: Number of sessions with protocol "IKEv2" logged off : 0

  Note: Using this command will force all existing IPsec IKEv2 VPN tunnels to be torn down. This will cause intermittent packet loss across the affected VPN tunnels until those tunnels are re-established.

  While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

• 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:
  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.

  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 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 Critical or High SIR vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.

  ASA Software

  Cisco ASA Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  9.7 and earlier1	Not vulnerable.	Migrate to a fixed release.
  9.8	Not vulnerable.	9.8.4.44 (June 2022)
  9.91	Not vulnerable.	Migrate to a fixed release.
  9.101	Not vulnerable.	Migrate to a fixed release.
  9.12	9.12.4.37	9.12.4.38
  9.131	Migrate to a fixed release.	Migrate to a fixed release.
  9.14	9.14.3.13	9.14.4
  9.15	9.15.1.21	9.15.1.21
  9.16	9.16.2.7	9.16.2.14
  9.17	Not vulnerable.	9.17.1.7

  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 this vulnerability.

  
  

  FTD Software

  Cisco FTD Software Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories
  6.2.2 and earlier1	Not vulnerable.	Migrate to a fixed release.
  6.2.3	Not vulnerable.	Migrate to a fixed release.
  6.3.01	Not vulnerable.	Migrate to a fixed release.
  6.4.0	6.4.0.13	6.4.0.15
  6.5.01	Migrate to a fixed release.	Migrate to a fixed release.
  6.6.0	6.6.5.1	6.6.5.2
  6.7.0	Cisco_FTD_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_FP1K_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_FP2K_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_Hotfix_AA-6.7.0.4-2.sh.REL.tar	Migrate to a fixed release.
  7.0.0	7.0.2	7.0.2
  7.1.0	Not vulnerable.	7.1.0.1

  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 vulnerability that is described in this advisory.

Source

• This vulnerability was found during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ipsec-mitm-CKnLr4

Revision History

• Version	Description	Section	Status	Date
  1.1	Updated ASA 9.8 first fixed release information.	Fixed Software	Final	2022-JUN-01
  1.0	Initial public release.	-	Final	2022-APR-27

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