Summary

• A vulnerability in the implementation of the Resource Public Key Infrastructure (RPKI) feature of Cisco IOS XR 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 specifically 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-xrbgp-rpki-dos-gvmjqxbk

  This advisory is part of the September 2021 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Cisco IOS XR Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco devices if they were running Cisco IOS XR Software releases 4.3.0 through 7.3.0 and had RPKI configured and in use.

  See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  Determine the RPKI Device Configuration

  To determine if an RPKI server is configured, issue the show running-config router bgp CLI command. If the rpki server command is displayed, as shown in the following example, the device could be vulnerable:

  iosxr# show running-config router bgp
  .
  .
  .
   rpki server 192.168.1.100

  Then, to determine if there is an active RPKI server, issue the show bgp rpki server summary CLI command. If an RPKI server TCP connection is in ESTAB state, as shown in the following example, the device is affected by this vulnerability:

  iosxr# show bgp rpki server summary
  Wed Aug 13 13:25:04.368 utc
  
  Hostname/Address        Transport       State           Time            ROAs (IPv4/IPv6)
  10.112.255.14           TCP:323         CONNECT         00:00:06        N/A
  2001:400:6:1::1         TCP:323         ESTAB           01:06:51        181152/30503
  

  Note: If the command does not return output, RPKI is not configured. However, if the command returns output but none of the RPKI servers have a connection in ESTAB state, the device could become vulnerable if the connection becomes established.

  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 XE Software
  • 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.

  Fixed Releases

  At the time of publication, the following Cisco IOS XR Software releases contained the fix for this vulnerability:

  • 7.3.1 and later
  • 7.3.15 and later
  • 7.4.1 and later

  At the time of publication, Cisco had released the following SMUs to address this vulnerability. Customers who require SMUs for platforms or releases that are not listed are advised to contact their support organization.

  Cisco IOS XR Software Release	Platform	SMU Name
  6.5.3	ASR9K-PX	asr9k-px-6.5.3.CSCvx04451
  6.7.4	CRS-PX	hfr-px-6.7.4.CSCvx04451
  7.0.2	ASR9K-X64	asr9k-x64-7.0.2.CSCvx04451
  7.1.2	ASR9K-X64	asr9k-x64-7.1.2.CSCvx04451

  See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information, including SMU availability.

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-xrbgp-rpki-dos-gvmjqxbk

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2021-SEP-08

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