Summary

• A vulnerability in Security Group Tag Exchange Protocol (SXP) in Cisco IOS Software, Cisco IOS XE Software, and Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.

  The vulnerability exists because crafted SXP packets are mishandled. An attacker could exploit this vulnerability by sending specifically crafted SXP packets to the affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a 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-sxp-68TEVzR

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE Software with an SXP peer connection configured.

  This vulnerability also affects the following Cisco devices that are running Cisco NX-OS Software with support for SXP version 4 (SXPv4):

  • Nexus 7000 Series Switches - Release 8.0(1) only
  • Nexus 1000 Virtual Edge for VMware vSphere
  • Nexus 1000V Switch for VMware vSphere

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

  Determine Whether an SXP Peer Connection Is Configured

  To determine whether a device is configured with an SXP peer connection, administrators can use the show running-config | include cts sxp command in the CLI and look for the presence of the cts sxp connection peer as shown in the following example:

  Router# show running-config | include cts sxp 
  cts sxp enable
  cts sxp connection peer 192.168.0.1 password none mode local listener hold-time 0 0
  Router#

  Devices that are configured with SXP peers in listener mode or both mode are vulnerable. Devices that are configured with SXP peers in speaker mode are not affected.

  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 XR Software.

Details

• To exploit this vulnerability, the attacker would need to know the SXP password if an SXP password is configured on the peers. The attacker also must be in a position to do the following successfully:

  • Source the traffic from the configured peer IP address
  • Target the traffic at the SXP listening IP address
  • Complete the TCP three-way handshake

Workarounds

• There are no workarounds that address this vulnerability.

  Customers who are using SXP connection peers are advised to protect them with a password. For more information, see the Cisco TrustSec Switch Configuration Guide.

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.

  Cisco NX-OS Software

  To help customers determine their exposure to vulnerabilities in Cisco NX-OS Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific Cisco NX-OS Software release and the earliest release that fixes the vulnerabilities that are 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, platform, 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 or one or more specific advisories.

  Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by choosing the Cisco NX-OS Software and platform and then entering a release-for example, 7.0(3)I7(5) for Cisco Nexus 3000 Series Switches or 14.0(1h) for Cisco NX-OS Software in ACI mode:

  Cisco NX-OS Software Cisco NX-OS Software in ACI Mode MDS 9000 Series Multilayer Switches Nexus 1000V Series Switches Nexus 3000 Series Switches Nexus 5000 Series Switches Nexus 6000 Series Switches Nexus 7000 Series Switches Nexus 9000 Series Switches

  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 and check the Medium check box in the drop-down list under Impact Rating when customizing a search.

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

• Cisco would like to thank FSTEC (https://fstec.ru/en) for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sxp-68TEVzR

Revision History

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

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