A vulnerability in the Cisco Discovery Protocol feature of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to execute arbitrary code as root or cause a denial of service (DoS) condition on an affected device. The vulnerability exists because of insufficiently validated Cisco Discovery Protocol packet headers. An attacker could exploit this vulnerability by sending a crafted Cisco Discovery Protocol packet to a Layer 2-adjacent affected device. A successful exploit could allow the attacker to cause a buffer overflow that could allow the attacker to execute arbitrary code as root or cause a DoS condition on the affected device. 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). Note: This vulnerability is different from the following Cisco FXOS and NX-OS Software Cisco Discovery Protocol vulnerabilities that Cisco announced on Feb. 5, 2020: Cisco FXOS, IOS XR, and NX-OS Software Cisco Discovery Protocol Denial of Service Vulnerability and Cisco NX-OS Software Cisco Discovery Protocol Remote Code Execution Vulnerability. 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200226-fxos-nxos-cdp This advisory is part of the February 2020 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication, which includes six Cisco Security Advisories that describe six vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: February 2020 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.
A vulnerability in the Cisco Discovery Protocol feature of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to execute arbitrary code as root or cause a denial of service (DoS) condition on an affected device.
The vulnerability exists because of insufficiently validated Cisco Discovery Protocol packet headers. An attacker could exploit this vulnerability by sending a crafted Cisco Discovery Protocol packet to a Layer 2-adjacent affected device. A successful exploit could allow the attacker to cause a buffer overflow that could allow the attacker to execute arbitrary code as root or cause a DoS condition on the affected device.
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).
Note: This vulnerability is different from the following Cisco FXOS and NX-OS Software Cisco Discovery Protocol vulnerabilities that Cisco announced on Feb. 5, 2020: Cisco FXOS, IOS XR, and NX-OS Software Cisco Discovery Protocol Denial of Service Vulnerability and Cisco NX-OS Software Cisco Discovery Protocol Remote Code Execution Vulnerability.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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200226-fxos-nxos-cdp
This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco FXOS Software or Cisco NX-OS Software and if they are configured to use Cisco Discovery Protocol:
Note: Cisco Discovery Protocol is enabled by default both globally and on all interfaces in Cisco FXOS and NX-OS Software.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
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 as well.
Administrators can determine whether Cisco Discovery Protocol is enabled on a device by using 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:
Vulmon
nxos# show running-config cdp all | include "cdp enable"
cdp enable
cdp enable
Cisco Discovery Protocol is always enabled on Ethernet uplink ports (network interfaces that connect to upstream switches for network connectivity), Ethernet port channel members, FCoE uplink ports, and management ports.
Administrators can determine whether Cisco Discovery Protocol is also 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 NFS storage) on a device by using 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, and if the command returns enable cdp under the eth-storage scope, Cisco Discovery Protocol is enabled on appliance ports, as shown in the following example:
ucs-fi# show configuration | egrep "^ scope|enable cdp"
.
.
.
scope org
enable cdp
.
.
.
scope eth-storage
enable cdp
.
.
.
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 products:
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.
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.
To disable Cisco Discovery Protocol globally on Cisco Nexus Switches that are running Cisco NX-OS Software, administrators can 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.
To disable Cisco Discovery Protocol on an interface on Cisco Nexus Switches that are running Cisco NX-OS Software, administrators can 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.
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, administrators can 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, administrators can 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#
Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts 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.
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
In the following table(s), the left column lists Cisco software releases. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.
Firepower 4100 Series and Firepower 9300 Security Appliances: CSCvr37151
| Cisco FXOS Software Release | First Fixed Release for This Vulnerability | First Fixed Release for all Vulnerabilities Described in the Bundle of Advisories |
|---|---|---|
| Earlier than 2.2 | Migrate to a fixed release. |
Migrate to a fixed release. |
| 2.2 | Migrate to a fixed release. | Migrate to a fixed release. |
| 2.3 | 2.3.1.179 | 2.3.1.179 |
| 2.4 | Migrate to a fixed release. | Migrate to a fixed release. |
| 2.6 | 2.6.1.187 | 2.6.1.187 |
| 2.7 | 2.7.1.106 | 2.7.1.106 |
Note: In Cisco FXOS Software releases 2.1 and later, this vulnerability is exploitable only via the management (mgmt0) port. In these releases Cisco Discovery Protocol is never actually enabled on front-panel ports, even if it is configured.
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:
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.
In the following table(s), the left column lists Cisco software releases. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.
UCS 6200 and 6300 Series Fabric Interconnects: CSCvr37150
| Cisco UCS Software Release | First Fixed Release for This Vulnerability | First Fixed Release for all Vulnerabilities Described in the Bundle of Advisories |
|---|---|---|
| Earlier than 3.2 | Migrate to a fixed release. | Migrate to a fixed release. |
| 3.2 | 3.2(3n) | 3.2(3n) |
| 4.0 | 4.0(4g) | 4.0(4g) |
| 4.1 | Not vulnerable. | Not vulnerable. |
For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, administrators can refer to the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.
To determine the best release for Cisco UCS, see the Recommended Releases documents in the release notes for the device.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
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.
This vulnerability was found during the resolution of a Cisco TAC support case.
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.1 | Added FXOS release. | Fixed Software | Final | 2020-March-06 |
| 1.0 | Initial public release. | - | Final | 2020-FEB-26 |
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