Summary

• A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the Cisco Discovery Protocol process to reload on an affected device.

  This vulnerability is due to a heap buffer overflow in certain Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a heap overflow, which could cause the Cisco Discovery Protocol process to reload on the device. The bytes that can be written in the buffer overflow are restricted, which limits remote code execution.

  Note: Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).  

  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-xr-cdp-wnALzvT2

  This advisory is part of the September 2022 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 2022 Semiannual 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 a vulnerable release of Cisco IOS XR Software and had the Cisco Discovery Protocol feature enabled.

  Note: Cisco Discovery Protocol is not enabled in Cisco IOS XR Software by default.

  For information about which Cisco software releases were vulnerable at the time of publication, see the Fixed Software section of this advisory. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  Determine the Status of Cisco Discovery Protocol

  To determine whether Cisco Discovery Protocol is enabled on a device, use the show running-config | include cdp command in the device CLI. If the command returns at least the following lines, Cisco Discovery Protocol is enabled globally and on at least one interface:

  RP/0/RP0/CPU0:ios##show running-config | include cdp
  Mon Dec  2 17:00:27.921 UTC
  Building configuration...
  cdp
  cdp
  .
  .
  .
  

  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, customers who do not use the Cisco Discovery Protocol feature can disable it either globally to fully close the attack vector or on individual interfaces to reduce the attack surface.

  Disable Cisco Discovery Protocol Globally

  To disable Cisco Discovery Protocol globally on devices that are running Cisco IOS XR Software, use the no cdp command in global configuration mode, as shown in the following example:

  RP/0/RP0/CPU0:iosxr#conf t
  Mon Sep 23 17:58:08.556 UTC
  RP/0/RP0/CPU0:iosxr(config)#no cdp       
  RP/0/RP0/CPU0:iosxr(config)#exit
  Uncommitted changes found, commit them before exiting(yes/no/cancel)? [cancel]:yes

  Disable Cisco Discovery Protocol on an Interface

  To disable Cisco Discovery Protocol on an interface on devices that are running Cisco IOS XR Software, use the no cdp command in interface configuration mode, as shown in the following example:

  RP/0/RP0/CPU0:iosxr#conf t
  Mon Sep 23 18:00:08.622 UTC
  RP/0/RP0/CPU0:iosxr(config)#interface GigabitEthernet0/0/0/0
  RP/0/RP0/CPU0:iosxr(config-if)#no cdp
  RP/0/RP0/CPU0:iosxr(config-if)#end
  Uncommitted changes found, commit them before exiting(yes/no/cancel)? [cancel]:yes

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

  The left column lists Cisco software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

  Cisco IOS XR Release	First Fixed Release
  5.2.2 and later	7.5.2 7.6.2 7.7.1

  The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

Exploitation and Public Announcements

• The Cisco PSIRT is aware that proof-of-concept exploit code is available for the vulnerability described in this advisory.

  The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.

Source

• Cisco would like to thank Qian Chen (@cq674350529) from Codesafe Team of Legendsec at QI-ANXIN Group for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xr-cdp-wnALzvT2

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2022-SEP-14

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