Cisco Security Advisory
Cisco IOS and IOS XE Software Autonomic Networking Infrastructure Denial of Service Vulnerability
A vulnerability in the Autonomic Networking feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause autonomic nodes of an affected system to reload, resulting in a denial of service (DoS) condition.
The vulnerability is due to an unknown condition in the Autonomic Networking code of the affected software. An attacker could exploit this vulnerability by replaying captured packets to reset the Autonomic Control Plane (ACP) channel of an affected system. A successful exploit could allow the attacker to reset the ACP channel of an affected system and consequently cause the affected device to reload, resulting in a DoS condition.
Cisco has not released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This vulnerability affects devices that are running any release of Cisco IOS or Cisco IOS XE Software that supports Autonomic Networking and are configured to use Autonomic Networking.
For more information about which Cisco IOS and IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.
Assessing the Autonomic Networking Configuration
To determine whether a device is configured to use Autonomic Networking, administrators can use the show running-config | include ^autonomic command in the CLI. The following example shows the output of the command for a device that is running Cisco IOS Software and is configured to use Autonomic Networking:
If a device is not configured to use Autonomic Networking, the command will not return any output.
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 identifies a Cisco product that is running Cisco IOS Software Release 15.5(2)T1 with an installed image name of C2951-UNIVERSALK9-M :
For information about the naming and numbering conventions for Cisco IOS Software releases, see White Paper: 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 XE Software or similar text.
The following example shows the output of the show version command on a device that is running Cisco IOS XE Software Release 3.16.1aS:
For information about the naming and numbering conventions for Cisco IOS XE 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 XR Software or Cisco NX-OS Software.
There are no workarounds that address this vulnerability.
Cisco has not released 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.
To help ensure a complete upgrade solution, customers may consider that this advisory is part of a collection that includes the following advisories:
- cisco-sa-20170726-aniacp. Cisco IOS and IOS XE Software Autonomic Control Plane Channel Information Disclosure Vulnerability
- cisco-sa-20170726-anicrl. Cisco IOS XE Software Autonomic Networking Infrastructure Certificate Revocation Vulnerability
- cisco-sa-20170726-anidos. Cisco IOS and IOS XE Software Autonomic Networking Infrastructure Denial of Service Vulnerability
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 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 or Cisco IOS XE Software release for example, 15.1(4)M2 or 3.1.4S in the following field:
Exploitation and Public Announcements
The Cisco Product Security Incident Response Team (PSIRT) is not aware of any malicious use of the vulnerability that is described in this advisory. Omar Eissa of ERNW disclosed this vulnerability during the Black Hat USA 2017 conference.
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Cisco Security Vulnerability Policy
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.
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