Cisco Security Advisory
Cisco IOS Software for Cisco Industrial Ethernet Switches PROFINET Denial of Service Vulnerability
A vulnerability in the implementation of the PROFINET Discovery and Configuration Protocol (PN-DCP) for Cisco IOS Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition.
The vulnerability is due to the improper parsing of ingress PN-DCP Identify Request packets destined to an affected device. An attacker could exploit this vulnerability by sending a crafted PN-DCP Identify Request packet to an affected device and then continuing to send normal PN-DCP Identify Request packets to the device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
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 September 27, 2017, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 12 Cisco Security Advisories that describe 13 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: September 2017 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 Software and are configured to process PROFINET messages. Beginning with Cisco IOS Software Release 12.2(52)SE, PROFINET is enabled by default on all the base switch module and expansion-unit Ethernet ports.
For information about which Cisco IOS Software releases are vulnerable, see the Fixed Software section of this advisory.
To determine whether the PROFINET feature is disabled, administrators can use the show running-config | include profinet command in the CLI and verify that the command returns output. The following example shows the output of the command for a device that is running Cisco IOS Software and is not configured to process PROFINET messages, which would indicate that the device is not vulnerable:
router# show running-config | include profinet no profinet
In addition, the administrator can use the show profinet status command in the CLI to determine if PROFINET is enabled. If the status of Profinet is Disabled or the command show profinet status does not exist on the hardware platform, the device is considered not vulnerable. In this example the PROFINET protocol is enabled:
router# show profinet status Profinet : Enabled
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 White Paper: Cisco IOS and NX-OS Software Reference Guide.
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XE Software, Cisco IOS XR Software, or Cisco NX-OS Software.
PROFINET is the PROFIBUS International (PI) open Industrial Ethernet Standard that uses TCP/IP and IT standards for automation control. PROFINET is particularly useful for industrial automation systems and process control networks, in which motion control and precision control of instrumentation and test equipment are important. It emphasizes data exchange and defines communication paths to meet speed requirements.
Exploitation of this vulnerability will cause an affected device to reload and generate a core file. Contact the Cisco Technical Assistance Center (TAC) to review the core file and determine whether the device has been compromised by exploitation of 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 Software
To help customers determine their exposure to vulnerabilities in Cisco IOS Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies any Cisco Security Advisories that impact a specific Cisco IOS 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 menu 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 Software release-for example, 15.1(4)M2-in the following field:
In March 2022, the Cisco Product Security Incident Response Team (PSIRT) became aware of additional attempted exploitation of this vulnerability in the wild. Cisco continues to strongly recommend that customers upgrade to a fixed software release to remediate this vulnerability.
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 1.2 Updated exploitation information. Exploitation and Public Announcements Final 2022-DEC-16 1.1 Added information to help administrators determine if Profinet is enabled. Vulnerable Products Final 2017-SEP-28 1.0 Initial public release. - Final 2017-SEP-27
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