Summary

• A vulnerability in the Raw Socket Transport feature of Cisco IOS XE 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 improper parsing of Raw Socket Transport payloads. An attacker could exploit this vulnerability by establishing a TCP session and then sending a malicious TCP segment via IPv4 to an affected device. This cannot be exploited via IPv6, as the Raw Socket Transport feature does not support IPv6 as a network layer protocol.

  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-20190925-rawtcp-dos

  This advisory is part of the September 25, 2019, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 12 Cisco Security Advisories that describe 13 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: September 2019 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASR 900 Series routers that are running Cisco IOS XE Software Release 16.9 and that are configured as a Raw Socket TCP Server. The Raw Socket TCP Server is not enabled in Cisco IOS XE Software by default.

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

  Determine Whether a Raw Socket TCP Server is Enabled

  To determine whether a Raw Socket TCP Server has been enabled, administrators can use the show raw-socket tcp detail | include Socket|listening command and look for a socket in listening state. The following example shows the output of the show raw-socket tcp detail | include Socket|listening command on a device that has a Raw Socket TCP Server enabled on port 2009 (the listening TCP port is configurable and may vary):

  ASR900#show raw-socket tcp detail | include Socket|listening
  --------------------------------------------- Socket Mapping --------------------------------------------
  Socket   status   interface  tty       vrf_name       hwidb     local_ip_addr  local_port   dest_ip_addr  dest_port
  [   0] listening    0/0/8    108                      76EE31E8  10.122.161.166       2009          ------      ----
  

  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 Cisco IOS Software, Cisco IOS XR Software, or Cisco NX-OS Software.

Indicators of Compromise

• A successful exploit of this vulnerability will cause an affected device to reload and generate a crashinfo file.

  A successful exploit of this vulnerability may be confirmed by decoding the stack trace for the device and determining whether the stack trace correlates with this vulnerability.

  Contact the Cisco Technical Assistance Center (TAC) to review the crashinfo file and determine whether the device has been compromised by exploitation of this vulnerability.

Workarounds

• There are no workarounds that address this vulnerability.

  To reduce the attack surface, administrators can use infrastructure access control lists (iACLs) on the interface to which the Raw Socket TCP Server is bound to restrict access to the Raw Socket TCP Server to trusted hosts only. Please refer to the Cisco Guide to Harden Cisco IOS Devices for further information on how to configure iACLs.

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 or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S-in the following field:

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

  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 the resolution of a Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190925-rawtcp-dos

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2019-September-25

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