Summary

• A vulnerability in the implementation of the Resource Public Key Infrastructure (RPKI) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the Border Gateway Protocol (BGP) process to crash, resulting in a denial of service (DoS) condition.

  This vulnerability is due to the incorrect handling of a specific RPKI to Router (RTR) Protocol packet header. An attacker could exploit this vulnerability by compromising the RPKI validator server and sending a specifically crafted RTR packet to an affected device. Alternatively, the attacker could use man-in-the-middle techniques to impersonate the RPKI validator server and send a crafted RTR response packet over the established RTR TCP connection to the affected device. A successful exploit could allow the attacker to cause a DoS condition because the BGP process could constantly restart and BGP routing could become unstable.

  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-rpki-dos-2EgCNeKE

  This advisory is part of the April 2022 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: April 2022 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco devices if they were running a vulnerable release of IOS XE Software and had the RPKI feature configured and in use.

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

  Determine Whether RPKI is Enabled

  To determine whether RPKI is enabled, issue the show bgp rpki servers command. If the command returns output, RPKI is enabled and the device is vulnerable. The following example shows the output of a device with RPKI configured with a server at the IP address 10.10.10.10 on port 10000:

  Router# show bgp rpki servers
  
  % Command accepted but obsolete, unreleased or unsupported; see documentation.
  
  BGP SOVC neighbor is 10.10.10.10/10000 connected to port 10000
  Flags 0, Refresh time is 600, Serial number is 0, Session ID is 0
  InQ has 0 messages, OutQ has 0 messages, formatted msg 0
  Session IO flags 0, Session flags 4000
   Neighbor Statistics:
  .
  .
  .
  
  Router#

  Note: The IP addresses displayed for configured neighbors depend on the device configuration.

  If the command returns no output, the device is not affected.

  Products Confirmed Not Vulnerable

  Cisco has confirmed that this vulnerability does not affect the following Cisco products:

  • IOS Software
  • IOS XR Software
  • Meraki products
  • NX-OS Software

Workarounds

• There are no workarounds that address this vulnerability.

  However, administrators can remove the RPKI configuration as a mitigation. If RPKI servers are either not in use or removed from the configuration, the device is considered not vulnerable. The decision to remove the RPKI configuration needs careful consideration.

  While this mitigation 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

• 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.

  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.

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 reported to the Cisco PSIRT for resolution by the U.S. National Security Agency (NSA).

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-rpki-dos-2EgCNeKE

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2022-APR-13

  Show Less