Cisco Security Advisory
Cisco IOS XE Software Encrypted Traffic Analytics Denial of Service Vulnerability
A vulnerability in the Cisco Encrypted Traffic Analytics (ETA) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to a logic error that exists when handling a malformed incoming packet, leading to access to an internal data structure after it has been freed. An attacker could exploit this vulnerability by sending crafted, malformed IP packets to an affected device. A successful exploit could allow the attacker to cause an 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 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 XE Software and are configured to use the Cisco ETA feature.
For information about which Cisco IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.
Assessing the Cisco Encrypted Traffic Analytics Configuration
Administrators can verify if a device is configured for ETA operation by using the show platform software et-analytics global CLI command. If the operations are configured, that command will list the configured interfaces in its output.
Here is an example of a device where ETA operation has been configured on the GigabitEthernet0/0/0 interface:
bsns-4331-4#show platform software et-analytics global
ET-Analytics Global state
All Interfaces : Off
IP Flow-record Destination: 192.0.2.2: 2055
Inactive timer: 15
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 Software, Cisco IOS XR Software, or Cisco NX-OS Software.
A vulnerability exists in the logic that is used by the Cisco ETA feature when processing malformed inbound packets on an interface configured for Cisco ETA operations. The logic error could cause an internal data structure to be freed while processing the packet. When the processing requires accessing the freed structure, an error occurs, and the device reloads.
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 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.
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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