Summary

• A vulnerability in the Cisco Discovery Protocol service of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause the service to restart, resulting in a denial of service (DoS) condition.

  This vulnerability is due to improper handling of Cisco Discovery Protocol messages that are processed by the Cisco Discovery Protocol service. An attacker could exploit this vulnerability by sending a series of malicious Cisco Discovery Protocol messages to an affected device. A successful exploit could allow the attacker to cause the Cisco Discovery Protocol service to fail and restart. In rare conditions, repeated failures of the process could occur, which could cause the entire device to restart.

  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-cdp-dos-G8DPLWYG

  This advisory is part of the February 2022 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: February 2022 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco FXOS or NX-OS Software:

  • Firepower 4100 Series (CSCvz72467)
  • Firepower 9300 Security Appliances (CSCvz72467)
  • MDS 9000 Series Multilayer Switches (CSCvz72463)
  • Nexus 1000 Virtual Edge for VMware vSphere (CSCvz72464)
  • Nexus 1000V Switch for Microsoft Hyper-V (CSCvz72464)
  • Nexus 1000V Switch for VMware vSphere (CSCvz72464)
  • Nexus 3000 Series Switches (CSCvz72442)
  • Nexus 5500 Platform Switches (CSCvz72465)
  • Nexus 5600 Platform Switches (CSCvz72465)
  • Nexus 6000 Series Switches (CSCvz72465)
  • Nexus 7000 Series Switches (CSCvz72463)
  • Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode (CSCvz72462)
  • Nexus 9000 Series Switches in standalone NX-OS mode (CSCvz72442)
  • UCS 6200 Series Fabric Interconnects (CSCvz74433)
  • UCS 6300 Series Fabric Interconnects (CSCvz74433)
  • UCS 6400 Series Fabric Interconnects (CSCvz72466)

  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 for Cisco FXOS Software

  Cisco Discovery Protocol is always enabled on the management (mgmt0) port. In Cisco FXOS Software releases earlier than Release 2.1, Cisco Discovery Protocol is always enabled on all front-panel ports.

  Determine the Status of Cisco Discovery Protocol on Cisco Nexus Switches that are Running Cisco NX-OS Software

  To determine whether Cisco Discovery Protocol is enabled on a device, use the show running-config cdp all | include "cdp enable" 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:

  nxos# show running-config cdp all | include "cdp enable"
  cdp enable
    cdp enable

  
  

  Determine the Status of Cisco Discovery Protocol on Cisco UCS Fabric Interconnects

  Cisco Discovery Protocol is always enabled on Ethernet uplink ports (network interfaces that connect to upstream switches for network connectivity), Ethernet port channel members, Fibre Channel over Ethernet (FCoE) uplink ports, and management ports.

  Cisco Discovery Protocol may also be enabled on server ports (interfaces that are presented to the servers in the Cisco UCS Manager domain) and appliance ports (interfaces that connect to directly attached Network File System (NFS) storage). To determine whether Cisco Discovery Protocol is enabled on server ports or appliance ports on a device, use the show configuration | egrep "^ scope|enable cdp" command in the device CLI. If the command returns the enable cdp command under the org scope, Cisco Discovery Protocol is enabled on server ports. If the command returns enable cdp under the eth-storage scope, Cisco Discovery Protocol is enabled on appliance ports. The following example shows the output for a device that has Cisco Discovery Protocol enabled on server ports and appliance ports:

  ucs-fi# show configuration | egrep "^ scope|enable cdp"
  .
  .
  .
   scope org
           enable cdp
  .
  .
  .
   scope eth-storage
           enable 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 Cisco Firepower 1000 Series and Cisco Firepower 2100 Series.

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 in Cisco FXOS Software

  Cisco Discovery Protocol is always enabled and cannot be disabled in Cisco FXOS Software. In Cisco FXOS Software releases 2.1 and later, Cisco Discovery Protocol is enabled on the management (mgmt0) port only.

  Disable Cisco Discovery Protocol Globally on Cisco Nexus Switches that are Running Cisco NX-OS Software

  To disable Cisco Discovery Protocol globally on Cisco Nexus Switches that are running Cisco NX-OS Software, use the no cdp enable command in global configuration mode, as shown in the following example:

  nxos# conf t
  Enter configuration commands, one per line. End with CNTL/Z.
  nxos(config)# no cdp enable 
  nxos(config)# end
  nxos# copy running-config startup-config 
  [########################################] 100%
  Copy complete.

  
  

  Disable Cisco Discovery Protocol on an Interface on Cisco Nexus Switches that are Running Cisco NX-OS Software

  To disable Cisco Discovery Protocol on an interface on Cisco Nexus Switches that are running Cisco NX-OS Software, use the no cdp enable command in interface configuration mode, as shown in the following example:

  nxos# conf t
  Enter configuration commands, one per line. End with CNTL/Z.
  nxos(config)# interface Ethernet1/1
  nxos(config-if)# no cdp enable 
  nxos(config-if)# end
  nxos# copy running-config startup-config
  [########################################] 100%
  Copy complete.

  
  

  Disable Cisco Discovery Protocol on Cisco UCS Fabric Interconnects

  Cisco Discovery Protocol cannot be disabled completely on Cisco UCS Fabric Interconnects.

  Cisco Discovery Protocol can be disabled on server ports and appliance ports on Cisco CS Fabric Interconnects, but it cannot be disabled on Ethernet uplink ports, Ethernet port channel members, FCoE uplink ports, or management ports.

  To disable Cisco Discovery Protocol on the server ports of a Cisco UCS Fabric Interconnect, use the disable cdp command in the default nw-ctrl-policy in the org scope, as shown in the following example:

  ucs-fi# scope org
  ucs-fi /org # enter nw-ctrl-policy default
  ucs-fi /org/nw-ctrl-policy # disable cdp
  ucs-fi /org/nw-ctrl-policy* # exit
  ucs-fi /org* # exit
  ucs-fi* # commit-buffer
  ucs-fi# 

  To disable Cisco Discovery Protocol on the appliance ports of a Cisco UCS Fabric Interconnect, use the disable cdp command in the default nw-ctrl-policy in the eth-storage scope, as shown in the following example:

  ucs-fi* # scope eth-storage
  ucs-fi /eth-storage* # enter nw-ctrl-policy default
  ucs-fi /eth-storage/nw-ctrl-policy* # disable cdp
  ucs-fi /eth-storage/nw-ctrl-policy* # exit
  ucs-fi /eth-storage* # exit
  ucs-fi* # commit-buffer
  ucs-fi# 

  While these mitigations have been deployed and were 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 FXOS Software

  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.

  Firepower 4100 Series and Firepower 9300 Security Appliances

  Cisco FXOS Software Release	First Fixed Release for This Vulnerability
  Earlier than 2.3	Migrate to a fixed release.
  2.3	2.3.1.219
  2.4	Migrate to a fixed release.
  2.5	Migrate to a fixed release.
  2.6	Migrate to a fixed release.
  2.7	Migrate to a fixed release.
  2.8	Migrate to a fixed release.
  2.9	2.9.1.158
  2.10	2.10.1.179
  2.11	Not vulnerable.

  
  

  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.

  Cisco Nexus 3000, 7000, and 9000 Series Switches SMUs

  Cisco has released the following SMUs to address this vulnerability. Customers can download the SMUs from the Software Center on Cisco.com.

  Cisco NX-OS Software Release	Platform	SMU Name
  7.0(3)I7(10)	Nexus 3000 and 9000 Series Switches	nxos.CSCvz72442-n9k_ALL-1.0.0-7.0.3.I7.10.lib32_n9000.rpm
  8.4(5)	Nexus 7000 Series Switches	n7000-s2-dk9.8.4.5.CSCvz72463.bin n7700-s2-dk9.8.4.5.CSCvz72463.bin n7700-s3-dk9.8.4.5.CSCvz72463.bin
  9.3(8)	Nexus 3000 and 9000 Series Switches	nxos.CSCvz72442-n9k_ALL-1.0.0-9.3.8.lib32_n9000.rpm

  For details about downloading and installing these SMUs, see the Performing Software Maintenance Upgrades section of the Cisco NX-OS system management configuration guide for Cisco Nexus 3000 Series Switches, Cisco Nexus 7000 Series Switches, or Cisco Nexus 9000 Series Switches.

  Cisco UCS Software

  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.

  UCS 6200, 6300, and 6400 Series Fabric Interconnects

  Cisco UCS Software Release	First Fixed Release for This Vulnerability
  Earlier than 4.0	Migrate to a fixed release.
  4.0	Migrate to a fixed release.
  4.1	4.1(3h)
  4.2	4.2(1l)1

  1. UCS Software release 4.2(1k) also contained the fix for this vulnerability. However, release 4.2(1k) is a deferred release.

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

  Additional Resources

  For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco MDS Series Switches
  Cisco Nexus 1000V for VMware Switch
  Cisco Nexus 3000 Series Switches
  Cisco Nexus 5500 Platform Switches
  Cisco Nexus 5600 Platform Switches
  Cisco Nexus 6000 Series Switches
  Cisco Nexus 7000 Series Switches
  Cisco Nexus 9000 Series Switches
  Cisco Nexus 9000 Series ACI-Mode Switches

  To determine the best release for Cisco UCS Software, see the Recommended Releases documents in the release notes for the device.

Exploitation and Public Announcements

• The Cisco 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 Hou JingYi of Qihoo 360 CERT for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cdp-dos-G8DPLWYG

Revision History

• Version	Description	Section	Status	Date
  1.1	Corrected defect information related to Nexus 9000 Series Fabric Switches.	Affected Products	Final	2022-MAR-01
  1.0	Initial public release.	-	Final	2022-FEB-23

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