A vulnerability in the processing of IP Service Level Agreement (SLA) packets by Cisco IOS Software and Cisco IOS XE software could allow an unauthenticated, remote attacker to cause an interface wedge and an eventual denial of service (DoS) condition on the affected device. The vulnerability is due to improper socket resources handling in the IP SLA responder application code. An attacker could exploit this vulnerability by sending crafted IP SLA packets to an affected device. An exploit could allow the attacker to cause an interface to become wedged, resulting in an eventual denial of service (DoS) condition on the affected device. 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-20190327-ipsla-dos 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.
A vulnerability in the processing of IP Service Level Agreement (SLA) packets by Cisco IOS Software and Cisco IOS XE software could allow an unauthenticated, remote attacker to cause an interface wedge and an eventual denial of service (DoS) condition on the affected device.
The vulnerability is due to improper socket resources handling in the IP SLA responder application code. An attacker could exploit this vulnerability by sending crafted IP SLA packets to an affected device. An exploit could allow the attacker to cause an interface to become wedged, resulting in an eventual denial of service (DoS) condition on the affected device.
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-20190327-ipsla-dos
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 routers that are running vulnerable releases of Cisco IOS and IOS XE Software and have been configured for IP SLA Responder operations.
For information about which Cisco IOS and IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.
Administrators can verify whether IP SLA Responder is in use on a device by verifying that it is reported as "Enabled" in the output of the show ip sla responder CLI command.
Here is an example of the output of that command on a router configured for IP SLA Responder operations:
Vulmon
Router#show ip sla responder
General IP SLA Responder on Control port 1967
General IP SLA Responder on Control V2 port 1167
General IP SLA Responder is: Enabled
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.
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.
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.Consult the Workarounds section of this advisory for more information about queue wedges and some detection mechanisms that may be used to identify a blocked interface in Cisco IOS Software. Also see the Cisco Security Blog Cisco IOS Queue Wedges Explained.
There are no workarounds that address this vulnerability.
The following identification mechanisms exist for 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:
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.
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:
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 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 |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2019-March-27 |
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