Summary

• A vulnerability in the Zone-Based Firewall code of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a device to reload.
  
  The vulnerability is due to the way fragmented packets are handled in the firewall code. An attacker could exploit this vulnerability by sending fragmented IP Version 4 or IP Version 6 packets through an affected device. An exploit could allow the attacker to cause the device to crash, resulting in a denial of service (DoS) condition.
  
  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-20180328-fwip

  This advisory is part of the March 28, 2018, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 20 Cisco Security Advisories that describe 22 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software and are configured with Zone-Based Policy Firewall.

  The following releases of Cisco IOS XE Software are vulnerable:

  • Everest-16.4.1
  • Everest-16.4.2
  • Everest-16.5.1
  • Everest-16.5.1b
  • Everest-16.6.1
  • Everest-16.6.1a

  To determine whether a device is configured with Zone-Based Policy Firewall, administrators can log in to the device and use the show zone security command in the CLI. If the command output shows a member interface under a zone name, the device is vulnerable.

  The following example shows the output of the command for a device that has Zone-Based Policy Firewall rules configured on both the GigabitEthernet0/0 and GigabitEthernet0/1 member interfaces:

  Router# show zone security
  zone self
    Description: System defined zone
  
  zone inside
    Description: *** Inside Network ***
    Member Interfaces:
      GigabitEthernet0/0
  
  zone outside
    Description: *** Outside Network ***
    Member Interfaces:
      GigabitEthernet0/1
  
  Router#

  Determining the Cisco IOS XE Software Release

  To determine which Cisco IOS XE Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XE Software, the system banner displays Cisco IOS Software, Cisco IOS XE Software, or similar text.

  The following example shows the output of the command for a device that is running Cisco IOS XE Software Release 16.2.1 and has an installed image name of CAT3K_CAA-UNIVERSALK9-M:

  ios-xe-device# show version
  
  Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2016 by Cisco Systems, Inc.
  Compiled Sun 27-Mar-16 21:47 by mcpre
  .
  .
  .

  For information about the naming and numbering conventions for Cisco IOS XE Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.
  
  Cisco has confirmed that this vulnerability does not affect Cisco IOS Software, Cisco IOS XR Software, or Cisco NX-OS Software.

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 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.

  Cisco IOS and IOS XE Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies 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 this tool to perform the following tasks:

  • Initiate a search by choosing one or more releases from a drop-down list or uploading a file from a local system for the tool to parse
  • Enter the output of the show version command for the tool to parse
  • Create a custom search by including all previously published Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication

  To determine whether a release is affected by any published Cisco Security Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS Software or Cisco IOS XE Software release—for example, 15.1(4)M2 or 3.13.8S—in the following field:

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-20180328-fwip

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2018-March-28

  Show Less