CVE-2022-20625: Cisco Security Advisory: Cisco FXOS and NX-OS Software Cisco Discovery Protocol Service Denial of Service Vulnerability

• 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.

• 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:

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.