Summary

• A vulnerability in the Event Management Service daemon (emsd) of Cisco IOS XR routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device.
  
  The vulnerability is due to improper handling of gRPC requests. An attacker could exploit this vulnerability by repeatedly sending unauthenticated gRPC requests to the affected device. A successful exploit could allow the attacker to crash the device in such a manner that manual intervention is required to recover.
  
  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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170503-ios-xr

Affected Products

• The vulnerability requires that the gRPC service is enabled on the affected device.
  
  The following example shows the output of the show running-config | include grpc CLI command on a device with the gRPC service enabled and configured:
  
  

  Router# show running-config | include grpc
          grpc
          !

  
  Determining the IOS XR Software Release
  
  To determine which Cisco IOS XR Software release is running on a device and the name of the device on which it is running, administrators can log in to the device and use the show version command in the command-line interface (CLI). If the device is running Cisco IOS XR Software, Cisco IOS XR Software or similar text appears in the system banner. The name of the hardware product appears on the line after the location of the system image file.
  
  The following example shows the output of the show version command on a device that is running Cisco IOS XR Software Release 5.2.5:
  
  

  RP/0/RP0/CPU0:ios#show version
  Wed Jun 15 16:08:37.966 UTC
  
  Cisco IOS XR Software, Version 5.2.5
  Copyright (c) 2013-2014 by Cisco Systems, Inc.
  
  Build Information:
   Built By     : ahoang
   Built On     : Thu Mar 17 19:26:37 PDT 2016
   Build Host   : iox-lnx-006
   Workspace    : /auto/srcarchive16/production/5.2.5/all/workspace
   Version      : 5.2.5
   Location     : /opt/cisco/XR/packages/
  
  cisco NCS-6000 () processor 
  System uptime is 6 weeks, 6 days, 19 hours, 32 minutes

  
  

  Vulnerable Products

  This vulnerability affects all Cisco IOS XR platforms that are running release 6.1.1 of Cisco IOS XR Software when the gRPC service is enabled on the device. The gRPC service is not enabled by default.
  
  For information about which Cisco IOS XR Software releases are vulnerable, see the Fixed Software section of this advisory.

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.

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 upgrade 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.

  Fixed Releases

  This vulnerability has been corrected in Cisco IOS XR Software Releases 6.1.2 and later.
  
  Note that Cisco IOS XR Software Releases 5.x and 6.0.x are not affected by this vulnerability.

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 reported to Cisco by an internal testing team.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170503-ios-xr

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2017-May-03

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