Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2017.0776 Cisco IOS XE Software for Cisco ASR 920 Series Routers Zero Touch Provisioning Denial of Service Vulnerability 23 March 2017 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco ASR 920 Series Aggregation Services Routers Publisher: Cisco Systems Operating System: Cisco Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2017-3859 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-ztp - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco IOS XE Software for Cisco ASR 920 Series Routers Zero Touch Provisioning Denial of Service Vulnerability High Advisory ID: cisco-sa-20170322-ztp First Published: 2017 March 22 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCuy56385 CVSS Score: Base 8.6, Temporal 8.6 CVE-2017-3859 CWE-134 Summary A vulnerability in the DHCP code for the Zero Touch Provisioning feature of Cisco ASR 920 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a format string vulnerability when processing a crafted DHCP packet for Zero Touch Provisioning. An attacker could exploit this vulnerability by sending a specially crafted DHCP packet to an affected device. An exploit could allow the attacker to cause the device to reload, resulting in a denial of service (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: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-ztp 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 Vulnerable Products This vulnerability affects Cisco ASR 920 Series Aggregation Services Routers that are running an affected release of Cisco IOS XE Software and are listening on the DHCP server port. By default, the devices do not listen on the DHCP server port. For information about which Cisco IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory. To determine whether a device is listening on the DHCP server port, use the show ip sockets privileged EXEC command on the device. The following example shows the output of the show ip sockets command on a Cisco IOS XE device configured as a DHCP server and/or a DHCP relay agent. The Port 67 output confirms that the device is listening for DHCP server packets: ASR920# show ip sockets Proto Remote Port Local Port In Out Stat TTY OutputIF 17 0.0.0.0 0 192.168.0.1 18999 0 0 11 0 17 0.0.0.0 0 --any-- 67 0 0 22211 0 ASR920# 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. Indicators of Compromise Exploitation of this vulnerability will cause an affected device to reload and generate a crashinfo file. Contact the Cisco Technical Assistance Center (TAC) to review the file and determine whether the device has been compromised by exploitation of this vulnerability. The device may crash with the following message: UNIX-EXT-SIGNAL: Segmentation fault(11), Process = DHCPD Receive Workarounds There are no workarounds that address 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 https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-ztp 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. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. 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 iQIVAwUBWNMxIIx+lLeg9Ub1AQjo3g//eju1K4DcFLXm2T3frCFAJ3vfw9gj2f0c rtZOwE2Xzlzy+lEz3ZE8Zg/v61yW4egYK+ds95Qj8dTNBbKyfgUcc5dE+UkNEt/x F0adVhage4ukZrnTZczgfa04sAPQbPWcfIxSufsr8bj8GNfb1YYNT7pcgdtRPh6W acwl3nF1yRx+zoHTz+dCW1vtYhJBqW6QfVKRSvb4vFXYIXaiRNyP4G8mcaYHzpIU UjRD3It7k5Zzj5t7C7kS4ZFKj/COijJDBf3iKboVT1qaDwhQIkS/Rq23ahI4xrFp u81jUOEdDuW2L0BnIWJIk+UQvKPR7j0o0TV7ieenOKdpQMxO9yqElSoLBIaY+voe 1kc702wbrRC0BJHYJ32Oahp7gZ1G1j4J6hueyb2+a4CEjMuUvKM0zVyUnDEMKGWg SGNtNb/UFw04JVmN8pj3FEDLUjBItWGjTU7ebE9h6TeAQipdtHxkEH29dgwFXwJ2 TBqgBPAD7PYHBBD1lcfU9qGt+aQkr7oxqSXUcv7Z6EtbrV1ORu4SdBCytO5jz95j HRDqZpsdjqGNcIZ2DMA2BYltysssolaTH0wGHuIWYgitJnYK6ClQ907JZ+XwVzE2 //2C8aTPke7FzJe92JkxNYbzMUsXeZkjuw/iyen5UG9EpG83JeC0Z6O/P1OSlsH6 WtyAzgLdHug= =YAce -----END PGP SIGNATURE-----