Summary

• A vulnerability in the hardware crypto driver of Cisco IOS XE Software for Cisco 4300 Series Integrated Services Routers and Cisco Catalyst 9800-L Wireless Controllers could allow an unauthenticated, remote attacker to disconnect legitimate IPsec VPN sessions to an affected device.

  The vulnerability is due to insufficient verification of authenticity of received Encapsulating Security Payload (ESP) packets. An attacker could exploit this vulnerability by tampering with ESP cleartext values as a man-in-the-middle.

  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-iosxe-vpn-dos-edOmW28Z

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco 4300 Series Integrated Services Routers and Cisco Catalyst 9800-L Wireless Controllers that were running a vulnerable release of Cisco IOS XE Software and were configured for IPsec VPN.

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

  Determine Whether IPsec VPN Is Configured

  To determine whether IPsec VPN is configured on a device, administrators can use the show running-config | include ^interface|^ crypto map command in the CLI. The following example shows the output of the show running-config | include ^interface|^ crypto map command on a device that has an IPsec VPN enabled on interface GigabitEthernet1:

  iosxe#show running-config | include ^interface|^ crypto map
  interface GigabitEthernet1
   crypto map mycmap
  interface GigabitEthernet2

  Alternatively, administrators can also use the show crypto map command. If the output of the show crypto map command lists any interfaces, the device is vulnerable through those interfaces. The following example shows the output of the show crypto map command on a device that has an IPsec VPN enabled on interface GigabitEthernet1:

  iosxe#show crypto map
  Crypto Map IPv4 "mycmap" 10 ipsec-isakmp
  	Dynamic map template tag: mydyncmap
  	Interfaces using crypto map mycmap:
  		GigabitEthernet1

   

  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:

  • IOS Software
  • IOS XR Software
  • NX-OS Software

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• 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.

  Cisco IOS and IOS XE Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).

  Customers can use the Cisco Software Checker to search advisories in the following ways:

  • Choose the software and one or more releases
  • Upload a .txt file that includes a list of specific releases
  • Enter the output of the show version command

  After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.

  Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release—for example, 15.1(4)M2 or 3.13.8S:

  By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search.

  For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.

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 internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-vpn-dos-edOmW28Z

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2020-JUN-03

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