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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2017.0780 Cisco IOS XE Software Web User Interface Denial of Service Vulnerability 23 March 2017 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco IOS XE Publisher: Cisco Systems Operating System: Cisco Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2017-3856 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-webui - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco IOS XE Software Web User Interface Denial of Service Vulnerability High Advisory ID: cisco-sa-20170322-webui First Published: 2017 March 22 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCup70353 CVSS Score: Base 8.6, Temporal 8.6 CVE-2017-3856 CWE-399 Summary A vulnerability in the web user interface of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient resource handling by the affected software when the web user interface is under a high load. An attacker could exploit this vulnerability by sending a high number of requests to the web user interface of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. To exploit this vulnerability, the attacker must have access to the management interface of the affected software, which is typically connected to a restricted management network. 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: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-webui This advisory is part of the March 22, 2017, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes five Cisco Security Advisories that describe five vulnerabilities. All the vulnerabilities have a Security Impact Rating of High. For a complete list of the advisories and links to them, see Cisco Event Response: March 2017 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication. Affected Products Cisco IOS XE Software provides a web user interface that allows users to manage and monitor most aspects of a device by using an easy-to-read graphical interface. To access a device by using the interface, the interface must be enabled for the device and a persistent web user interface transport map must be configured and applied to the device. The transport map defines how the device handles incoming requests for the web user interface. Vulnerable Products This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software, if the web user interface of the software is enabled. By default, the web user interface is not enabled. For information about which Cisco IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory. Assessing the Web User Interface Configuration To determine whether the web user interface is enabled and configured for a device, administrators can log in to the device and use the CLI to check for the presence of the following commands... transport-map type persistent webui transport-map-name transport type persistent webui input transport-map-name ...in addition to the ip http server or ip http secure-server global configuration command. If those commands are present and configured, the web user interface is enabled and configured for the device. To determine whether those commands are present and configured, administrators can use the show running-config | include http|transport command in the CLI. The following example shows the output of the show running-config | include http|transport command for a router that is enabled and configured to use the web user interface: Router# show running-config | include http|transport transport-map type persistent webui https-webui transport-map type persistent webui http-webui no ip http server ip http authentication local ip http secure-server transport type persistent webui input http-webui 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: Router> show version Cisco IOS XE Software, Version 03.16.01a.S - Extended Support Release Cisco IOS Software, ASR1000 Software (PPC_LINUX_IOSD-ADVENTERPRISEK9-M), Version 15.5(3)S1a, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2015 by Cisco Systems, Inc. Compiled Wed 04-Nov-15 17:40 by mcpre . . . 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 Software, Cisco IOS XR Software, or Cisco NX-OS Software. Workarounds There are no workarounds that address this vulnerability. However, administrators can mitigate this vulnerability by disabling the web user interface for an affected device until the device is upgraded to a software release that addresses this vulnerability. Fixed Software 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: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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 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: http://www.cisco.com/en/US/support/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. 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 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 releasefor example, 15.1(4)M2 or 3.1.4Sin the following field: 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. Exploitation and Public Announcements 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. Source This vulnerability was found during the resolution of a support case. URL http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-webui Revision History Version Description Section Status Date 1.0 Initial public release. Final 2017-March-22 - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. 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If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBWNNQgYx+lLeg9Ub1AQgplg//WIr+f4VjzYSDr9/lIUwxgKr1K+RM+sod nejpfOFQTe01x/HgrsZ4fe3ENNhwpt57XTX/IbvtBV3QsS9jrBCXM4dnUD5FSSAz si/OC3FKUsdOdxYfiS8iIKbzoT0b78ya9n+D4inVAn5udkUrQVJBD4f0/Ut92zJi cVxa8u2DALTPT1IDMhtmhDtSjZWhB/829ebO/Glz9WAO1RKOXfe/PU+N0a178Kyk zoH3cMIGEpVrWjoOLf395ULLfoHd40Q3dOo2vylnn1m3qJ2c+9NyTKGQJA4ppcgs rh5nEaQv0XxgUCuxdhpSIVs1EhRoDNfz/CQdKK8OS0LeO0nA1huMmUam5JBoh+KF atajLnnlIcjDfrMTROBWm+LkzKcyC3wyFtGlb8aAlZwjsvQg8yjG+LHfAnQlvvlR jKPtlKH1cJsvSOKkJGKmK/ZnwW3sBtKQsKx0cSgioZlTlPdcf1qHeUHgK3+H+ncj ldzePVHEkZtfcUAYXSsjlmpKYhvmSV2iht0M1W1ClLQbTJXfl2AnmJoftQbE+8bC 8Xo+dZTk8ZZNoVFt66JQ4MR5MXyqX14FFbu8rRaCs5bXMkOs0rJ4i4Cdon/MDDAR 4M0Y8WZD9CzlnLxVkrxNxmDDtpZwpZSyuM7efsDQXmKGOtxcEltloSwVXy7qHq7O 5ePI1x8phIU= =3r1r -----END PGP SIGNATURE-----