Summary

• A vulnerability in the IP version 6 (IPv6) processing code of Cisco IOS XR Software for Cisco CRS-3 Carrier Routing System could allow an unauthenticated, remote attacker to trigger an ASIC scan of the Network Processor Unit (NPU) and a reload of the line card processing an IPv6 packet.
  
  The vulnerability is due to incorrect processing of an IPv6 packet carrying IPv6 extension headers that are valid but unlikely to be seen during normal operation. An attacker could exploit this vulnerability by sending such an IPv6 packet to an affected device that is configured to process IPv6 traffic. An exploit could allow the attacker to cause a reload of the line card, resulting in a DoS condition.
  
  Cisco has released software updates that address this vulnerability. There is no workaround that mitigates this vulnerability.
  
  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20150611-iosxr

Affected Products

• Vulnerable Products

  A Cisco CRS-3 Carrier Routing System device is affected by this vulnerability when all the following conditions are met:
  
  1) Any of the following line cards are installed on the chassis:
  

  • CRS-MSC-140G: Cisco CRS-3 Modular Services Card (140G)
  • CRS-FP140: Cisco CRS-3 Forwarding Processor Card (140 Gbps)
  • CRS-LSP: Cisco CRS-3 Label Switch Processor

  2) The Cisco CRS-3 Carrier Routing System device is running a Cisco IOS XR release affected by this vulnerability. See the "Software Versions and Fixes" section of this advisory for information about affected releases. Note: Cisco IOS XR Software Releases 4.2.1 and later are not affected by this vulnerability.
  

  3) Any previously listed line card is configured to process IPv6 traffic.

  Administrators can use the show diag command to determine whether any of the affected line cards are installed on a Cisco CRS-3 Carrier Routing System device. The following output shows a Cisco CRS-3 Carrier Routing System device with a CRS-MSC-140G line card installed:
  
  

  RP/0/RP0/CPU0:router#sh diag
  Thu Jun  4 14:53:25.229 EDT
  
  CARD 0/0/* : Cisco CRS Series Modular Services Card 140G
    MAIN:  board type 500064
           800-32942-06 rev B0
           dev N/A
           S/N SAX99999ZZZ
    PCA:   73-12720-06 rev A0
    PID:   CRS-MSC-140G
    VID:   V03
    CLEI:  IPUCAZYBAC
    ECI:   180032
  
  
   

  
  Administrators can use the show version command to determine the Cisco IOS XR release running on the device. A device running Cisco IOS XR will include the string "Cisco IOS XR" in the output of the show version command. The following example shows a device running Cisco IOS XR Release 4.1.2:
  

  RP/0/RP0/CPU0:router#sh version 
  Thu Jun  4 14:56:06.484 EDT
  
  Cisco IOS XR Software, Version 4.1.2[Default]
  Copyright (c) 2012 by Cisco Systems, Inc.
  
  ROM: System Bootstrap, Version 2.05(20110622:151317) [CRS ROMMON],  
  
  router uptime is 2 years, 11 weeks, 5 days, 10 hours, 22 minutes
  
  System image file is "disk0:hfr-os-mbi-4.1.2.CSCtw71819-1.0.0/0x100008/mbihfr-rp-x86e.vm"
  
  cisco CRS-16/S (Intel 686 F6M14S4) processor with 12582912K bytes of memory.
  Intel 686 F6M14S4 processor at 2130Mhz, Revision 2.174
  
  Cisco CRS Series 16 Slots Line Card Chassis
  
   

  
  Administrators can use the show ipv6 interface brief command to determine if an interface is enabled for IPv6 traffic processing. The following example shows an interface configured for IPv6 processing:
  

  RP/0/RP0/CPU0:router# show ipv6 interface brief
  
   
  GigabitEthernet0/2/0/0 [Up/Up]
  fe80::212:daff:fe62:c150
  202::1
   

  
  The show ipv6 interface brief command will produce an error message if the running version of Cisco IOS XR Software does not support IPv6. The output will not show any interfaces with IPv6 addresses if IPv6 is disabled.
  
  An interface may be configured for IPv6 processing but may not appear on the output of the show ipv6 interface brief command if the interface is part of a bundle or a virtual routing and forwarding (VRF) instance. The show ipv6 vrf all interface command can be used to determine whether any interface has been configured in this way. The following is the output of the show ipv6 vrf all interface command showing an interface configured for IPv6 processing as part of a bundle and assigned to a VRF instance:
  
  

  RP/0/RP0/CPU0:router#sh ipv6 vrf all interface 
  Thu Jun  4 15:12:11.170 EDT
  
  
  
  Bundle-Ether4.765 is Up, ipv6 protocol is Up, Vrfid is FDA (0x60000001)
    IPv6 is enabled, link-local address is fe80::21d:a2ff:aabb:ccdd
    Global unicast address(es):
      2001:db8:1:1::1, subnet is 2001:db8:1:1::/64 
    Joined group address(es): ff02::1:ff00:0 ff02::1:aabb:ccdd ff02::2
        ff02::1
    MTU is 1518 (1500 is available to IPv6)
    ICMP redirects are disabled
    ICMP unreachables are enabled
    ND DAD is enabled, number of DAD attempts 1
    ND reachable time is 0 milliseconds
    ND advertised retransmit interval is 0 milliseconds
    Hosts use stateless autoconfig for addresses.
    Outgoing access list is not set
    Inbound  access list is not set
    Table Id is 0xe0800001
  
  
  

  Products Confirmed Not Vulnerable

  Cisco 12000 Series Routers, Cisco ASR 9000 Series Aggregation Services Routers, Cisco Carrier Routing System 1 (CRS-1), Cisco CRS-X Carrier Routing System, and Cisco Network Convergence System 6000 Series Routers running Cisco IOS XR Software are not affected by this vulnerability. Only Cisco CRS-3 Carrier Routing System devices that meet all the conditions in the "Vulnerable Products" section of this advisory are affected by this vulnerability.
  
  No other Cisco products are currently known to be affected by this vulnerability.

Details

• A vulnerability in the IP version 6 (IPv6) processing code of Cisco IOS XR Software for Cisco CRS-3 Carrier Routing System could allow an unauthenticated, remote attacker to trigger an ASIC scan of the Network Processor Unit (NPU) and a reload of the line card processing an IPv6 packet.
  
  The vulnerability is due to incorrect processing of an IPv6 packet carrying IPv6 extension headers that are valid but unlikely to be seen during normal operation. An attacker could exploit this vulnerability by sending such an IPv6 packet to an affected device that is configured to process IPv6 traffic. An exploit could allow the attacker to cause a reload of the line card, resulting in a DoS condition.
  
  A Cisco CRS-3 Carrier Routing System device that meets all the conditions listed in the "Vulnerable Products" section of this advisory is affected by this vulnerability.
  
  This vulnerability can be triggered by IPv6 transit traffic or IPv6 traffic destined to the device itself.
  
  This vulnerability could be exploited repeatedly to cause an extended DoS condition.
  
  This vulnerability has been documented in Cisco bug ID CSCtx03546 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2015-0769.

Workarounds

• There is no workaround that mitigates this vulnerability.
  

Fixed Software

• When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Alerts archive at http://www.cisco.com/go/psirt and review subsequent advisories 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.
  
  The following Cisco IOS XR releases are affected by this vulnerability:

  • Cisco IOS XR Releases 4.0.1, 4.0.2, 4.0.3 and 4.0.4
  • Cisco IOS XR Releases 4.1.0, 4.1.1 and 4.1.2
  • Cisco IOS XR Release 4.2.0

  This vulnerability has been corrected in the following Software Maintenance Updates (SMUs):

  • hfr-px-4.1.0.CSCtx03546.pie for release 4.1.0
  • hfr-px-4.1.1.CSCtx03546.pie for release 4.1.1
  • hfr-px-4.1.2.CSCtx03546.pie for release 4.1.2
  • hfr-px-4.2.0.CSCtx03546.pie for release 4.2.0

  Please consult the README file associated with each SMU for additional information.

  Customers running Cisco IOS XR Releases 4.0.1, 4.0.2, 4.0.3, or 4.0.4 should upgrade to a currently supported release.
  
  Cisco IOS XR Release 4.2.1 and later already include a fix for this vulnerability. No upgrade or SMU installation will be required.

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.

  This vulnerability was found by Cisco internally.
  

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20150611-iosxr

Revision History

• Revision 1.0

  2015-June-11

  Initial public release

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