Cisco IOS XR Software IPv6 Malformed Packet Denial of Service Vulnerability

Summary

• 
  A vulnerability in the parsing of malformed Internet Protocol version 6 (IPv6) packets in Cisco IOS XR Software for ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a lockup and eventual reload of a Network Processor (NP) chip and a line card processing traffic. Only Trident-based line cards on Cisco ASR 9000 Series Aggregation Services Routers are affected by this vulnerability.
  
  The vulnerability is due to insufficient logic in parsing malformed IPv6 packets. An attacker could exploit this vulnerability by sending a stream of malformed IPv6 packets to the affected device. An exploit could allow the attacker to cause a lockup and eventual reload of an NP chip and a line card, leading to 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:
  http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140611-ipv6

Affected Products

• Vulnerable Products

  
  Cisco ASR 9000 Series Routers with Trident-based line cards are affected by this vulnerability. The device does not have to be configured with IPv6 to be affected by this vulnerability.
  
  The first generation of the Cisco ASR 9000 Series Ethernet line cards are referred to as Trident-based line cards. The term comes from the NPs that are used on these line cards.
  
  The following line cards are Trident based:
  
  

  • A9K-40GE-L
  • A9K-40GE-B
  • A9K-40GE-E
  • A9K-4T-L
  • A9K-4T-B
  • A9K-4T-E
  • A9K-8T/4-L
  • A9K-8T/4-B
  • A9K-8T/4-E
  • A9K-2T20GE-L
  • A9K-2T20GE-B
  • A9K-2T20GE-E
  • A9K-8T-L
  • A9K-8T-B
  • A9K-8T-E
  • A9K-16T/8-B

  
  To determine whether the line card on an ASR 9000 Series Router is Trident based, the administrator can use the show diag command. Affected devices will include the PID for at least one of the Trident-based cards. The following example shows the device on which an A9K-40GE-B card is active:
  
  

  RP/0/RSP0/CPU0:router(admin)# show diag
  
  Mon Jun 22 12:55:10.554 PST
  
  NODE module 0/RSP0/CPU0 : 
  
    MAIN:  board type 0x100302
  
  !--- output truncated
  
  NODE module 0/1/CPU0 :  
  
     MAIN:  board type 0x20207
    S/N:   FOC123081J6
    Top Assy. Number:   68-3182-03
    PID:   A9K-40GE-B
    UDI_VID:   V1D
    HwRev: V0.0
    New Deviation Number: 0
    CLEI:   
    Board State : IOS XR RUN
    PLD:    Motherboard: N/A, Processor: 0x8004 (rev: 2.2), Power: N/A
    ROMMON: Version 1.0(20081208:174521) [ASR9K ROMMON]
  
  !--- output truncated
  
  

  
  

  Products Confirmed Not Vulnerable

  
  Cisco ASR 9000 Series Routers with Typhoon-based line cards are not affected by this vulnerability.
  The second generation of the ASR 9000 Series Ethernet line cards are often referred to as Typhoon-based line cards.
  
  These line cards are Typhoon based:
  
  

  • A9K-MOD80-SE
  • A9K-MOD80-TR
  • A9K-MOD160-SE
  • A9K-MOD160-TR
  • A9K-24X10GE-SE
  • A9K-24X10GE-TR
  • A9K-36X10GE-SE
  • A9K-36X10GE-TR
  • A9K-2X100GE-SE
  • A9K-2X100GE-TR
  • A9K-1X100GE-SE
  • A9K-1X100GE-TR

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

Details

• A vulnerability in the parsing of malformed Internet Protocol version 6 (IPv6) packets in Cisco IOS XR Software for ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a lockup and eventual reload of a Network Processor (NP) chip and a line card processing traffic. Only Trident-based line cards on Cisco ASR 9000 Series Aggregation Services Routers are affected by this vulnerability.
  
  The vulnerability is due to insufficient logic in parsing malformed IPv6 packets. An attacker could exploit this vulnerability by sending a stream of malformed IPv6 packets to the affected device. An exploit could allow the attacker to cause a lockup and eventual reload of an NP chip and a line card, leading to a denial of service (DoS) condition.
  
  This vulnerability could be exploited repeatedly to cause an extended DoS condition.
  
  A device does not need to be configured for IPv6 functionality to be affected by this vulnerability. If interfaces on the Trident-based line card do not have IPv6 functionality enabled, the attacker can only send malformed traffic from an adjacent host. If a device has IPv6 functionality enabled, the vulnerability can be exploited from a remote network.
  
  While certain intermediate devices may block malformed IPv6 packets, the possibility still exists for a malformed packet to originate from a remote network and exploit this vulnerability on an affected device.
  
  This vulnerability has been documented in Cisco bug ID CSCun71928 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) CVE-2014-2176.
  
  
  

Workarounds

• There are no workarounds for this vulnerability.
  
  Additional mitigations that can be deployed on Cisco devices within the network are available in the companion document Identifying and Mitigating Exploitation of the Cisco IOS XR Software IPv6 Malformed Packet Denial of Service Vulnerability, which is available at the following link: http://tools.cisco.com/security/center/viewAMBAlert.x?alertId=33986

Fixed Software

• When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Notices 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.
  
  

  This vulnerability is corrected in the following Cisco IOS XR Software SMUs:
  
  

  • asr9k-p-4.1.2.CSCun71928 for version 4.1.2
  • asr9k-p-4.2.1.CSCun71928 and asr9k-px-4.2.1.CSCun71928 for version 4.2.1
  • asr9k-px-4.2.3.CSCun71928 and asr9k-p-4.2.3.CSCun71928 for version 4.2.3
  • asr9k-px-4.3.1.CSCun71928 for version 4.3.1
  • asr9k-px-4.3.2.CSCun71928 for version 4.3.2
  • asr9k-px-4.3.4.CSCuo22306 for version 4.3.4
  • asr9k-px-5.1.1.CSCuo22306 for version 5.1.1

  Cisco IOS XR Software Release 5.1.2 is not affected by this vulnerability.
  
  Note: Cisco IOS XR Software SMUs for additional versions will be published when available.

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 discovered by Cisco TAC during the investigation of customer cases.

  
  

URL

• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140611-ipv6

Revision History

• Revision 1.1	2014-June-13	Added information about 4.1.2-based SMU to the "Software Versions and Fixes" section.
  Revision 1.0	2014-June-11	Initial public release.

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