Cisco Security Advisory
Cisco IOS and IOS XE Software Network Plug-and-Play Agent Certificate Validation Vulnerability
A vulnerability in the Cisco Network Plug-and-Play (PnP) agent of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to gain unauthorized access to sensitive data.
The vulnerability exists because the affected software insufficiently validates certificates. An attacker could exploit this vulnerability by supplying a crafted certificate to an affected device. A successful exploit could allow the attacker to conduct man-in-the-middle attacks to decrypt and modify confidential information on user connections to the affected software.
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:
This advisory is part of the March 27, 2019, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 17 Cisco Security Advisories that describe 19 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: March 2019 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE Software with the Cisco Plug-and-Play (PnP) agent enabled and initiated.
The PnP agent is enabled on all Cisco IOS and IOS XE Software platforms by default, but it is initiated only under one of the following conditions:
- The startup configuration is absent.
- A PnP profile has been configured and activated through the CLI.
For information about which Cisco IOS and IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.
Determining Whether a PnP Profile Has Been Configured
To determine whether a PnP profile has been configured, administrators can use the show pnp profile command in the CLI. The following example shows the output of the show pnp profile command with a PnP profile named test configured and activated:
Device# show pnp profile Initiator Profile test: 0 open connections: 0 closing connections Encap: xmpp11 WSSE header is not required. Configured authorization level is 1 Countdown: Security Unlock 0, Service Lock: 0, Service Req Wait: 0, Prxoy Req Wait 0, Service Resp Ack: 0 Max message (RX) is 50 Kbytes XEP Faults are sent Idle timeout infinite Keepalive not configured Reconnect time 60 seconds Primary transport: xmpp socket to host 172.19.193.60, port 5222 Not connected, next reconnect attempt in 52 seconds Device#
An empty output of this command indicates that no PnP profile has been configured.
In some releases of Cisco IOS and IOS XE Software, the output of the show pnp profile command is different. The following example shows the output of the show pnp profile command in these releases with a PnP profile named pnp-zero-touch configured and activated:
Device#show pnp profile PnP Profiles: Active:1, Created:1, Deleted:0, Hidden:0 Name CBType Node Primary-Path Primary-Trans Backup-Trans pnp-zero-touch User visible pnp/WORK-REQUEST HTTPS none Initiator Profile pnp-zero-touch: 0 open connections: 0 closing connections Encap: pnp WSSE header is not required. Configured authorization level is 1 . . . Max message (RX) is 50 Kbytes XEP Faults are sent Idle timeout infinite Keepalive not configured DNS Resolution: default Reconnect time 60 seconds Primary Transport:https to Host:-, IP:10.201.237.169, Port:443, Src-Intf:-, VRF:-, URL pnp/WORK-REQUEST Not connected, next reconnect attempt in 30 seconds . . .
In these releases, an output containing Active:0 indicates that no active PnP profile has been configured.
Determining the Cisco IOS Software Release
To determine which Cisco IOS Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS Software, the system banner displays text similar to Cisco Internetwork Operating System Software or Cisco IOS Software. The banner also displays the installed image name in parentheses, followed by the Cisco IOS Software release number and release name. Some Cisco devices do not support the show version command or may provide different output.
The following example shows the output of the command for a device that is running Cisco IOS Software Release 15.5(2)T1 and has an installed image name of C2951-UNIVERSALK9-M:
Router> show version Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2015 by Cisco Systems, Inc. Compiled Mon 22-Jun-15 09:32 by prod_rel_team . . .
For information about the naming and numbering conventions for Cisco IOS Software releases, see the Cisco IOS and NX-OS Software Reference Guide.
Determining the Cisco IOS XE Software Release
To determine which Cisco IOS XE Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XE Software, the system banner displays Cisco IOS Software, Cisco IOS XE Software, or similar text.
The following example shows the output of the command for a device that is running Cisco IOS XE Software Release 16.2.1 and has an installed image name of CAT3K_CAA-UNIVERSALK9-M:
ios-xe-device# show version Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compiled Sun 27-Mar-16 21:47 by mcpre . . .
For information about the naming and numbering conventions for Cisco IOS XE Software releases, see the Cisco IOS and NX-OS Software Reference Guide.
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 IOS XR Software or Cisco NX-OS Software.
There are no workarounds that address this vulnerability.
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:
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 Without Service Contracts
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:
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.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities 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 this tool to perform the following tasks:
- Initiate a search by choosing one or more releases from a drop-down list or uploading a file from a local system for the tool to parse
- Enter the output of the show version command for the tool to parse
- Create a custom search by including all previously published Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication
To determine whether a release is affected by any published Cisco Security Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S-in the following field:
By default, the Cisco IOS Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, use the Cisco IOS Software Checker on Cisco.com and check the Medium check box in the Impact Rating drop-down list.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.Note: Starting with Cisco IOS XE Software Release 16.9.1, any upgrade will require Smart Licensing. Customers who plan to upgrade Cisco IOS XE to Release 16.9.1 or later are advised to consider the Smart Licensing requirement. The following documentation provides additional information: Smart Licensing.
Note: Releases of Cisco IOS and IOS XE Software that contain the fix for this vulnerability require that the PnP server-provided certificate contains a valid Subject Alternative Name (SAN) field to verify the sever identity. The software compares the SAN field of this certificate to the PnP server DNS name or IP address that is configured in the PnP profile on the Cisco IOS or IOS XE device.
Customers using an on-premises Cisco Application Policy Infrastructure Controller Enterprise Module (APIC-EM) or Cisco Digital Network Architecture (DNA) Center as a PnP server must ensure that the PnP server certificate contains a valid SAN field. If it does not contain a valid SAN field, the administrator must generate a certificate signing request (CSR) that includes the appropriate SAN field, have the new certificate signed by their certificate authority (CA), and then install it on the PnP server.
Further details on how to obtain a CA-signed certificate for the Cisco APIC-EM are available in the Securing the Cisco APIC-EM chapter of the Cisco Application Policy Infrastructure Controller Enterprise Module Administrator Guide. Further details for Cisco DNA Center can be found in the Configure System Settings chapter of the Cisco Digital Network Architecture Center Administrator Guide.
Customers who require assistance to configure a self-signed certificate with a valid SAN field are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
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 internal security testing.
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 1.0 Initial public release. - Final 2019-March-27
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