Summary

• Multiple Multi Protocol Label Switching (MPLS) related vulnerabilities exist on Cisco IOSŪ XR. Only systems that are running Cisco IOS XR and configured for MPLS are affected by these vulnerabilities.

  Upon successful exploitation a Modular Services Card (MSC) on a Cisco Carrier Routing System 1 (CRS-1) or a Line Card (LC) on a Cisco 12000 series router may reload affecting switched traffic.

  Cisco has made free software available to address this vulnerability for affected customers.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060419-xr.

Affected Products

• This section provides details on affected products.

  Vulnerable Products

  Only systems that are running Cisco IOS XR and configured for MPLS are affected by this vulnerability.

  Systems that are running Cisco IOS XR and configured for MPLS can be identified by the show mpls interfaces command. A sample output of this command on a CRS-1 that is configured for MPLS is given below.

    RP/0/RP1/CPU0:crs1#show mpls interfaces
    Interface                  LDP      Tunnel   Enabled
    -------------------------- -------- -------- --------
    POS0/2/0/0                 Yes      Yes      Yes
    POS0/2/0/1                 No       Yes      Yes
    POS0/2/0/2                 Yes      No       Yes
    POS0/2/0/3                 Yes      Yes      Yes
    GigabitEthernet0/3/1/0     Yes      No       Yes
    GigabitEthernet0/3/1/3     Yes      No       Yes
    POS0/3/0/1                 Yes      Yes      Yes
    TenGigE0/6/0/0             Yes      No       Yes
    RP/0/RP1/CPU0:crs# 
  

  In the above output, the fourth column labeled Enabled identifies MPLS enabled interfaces.

  Products Confirmed Not Vulnerable

  Cisco IOS XR only runs on CRS-1 or Cisco 12000 series routers. Other Cisco products, including systems that run Cisco IOS are not affected.

Details

• Cisco IOS XR Software is a member of the Cisco IOS Software Family that uses a microkernel based distributed operating system infrastructure. Cisco IOS XR runs both on Cisco CRS-1 and Cisco 12000 series routers.

  More information on Cisco IOS XR can be found at the following URL:

  http://www.cisco.com/en/US/products/ps5845/index.html

  Modular Services Cards (MSC), also called the line cards are Layer-3 forwarding engines on Cisco CRS-1. An MSC is paired with a physical layer interface module (PLIM) which provides layer-1 and layer-2 services.

  More information on Cisco CRS-1 architecture can be found at the following URL:

  http://www.cisco.com/en/US/products/ps5763/index.html

  Specific MPLS packets that are switched by a Cisco CRS-1 or a 12000 series system will restart the NetIO process. If the NetIO process is restarted several times consecutively, the line card will reload causing a Denial of Service (DoS) condition for the traffic that is being switched on that line card.

  MPLS packets will be forwarded through the MPLS network. Therefore, packets that can trigger this vulnerability can be sent from remote systems that are in the MPLS network. Such packets can not be received on interfaces that are not configured for MPLS.

  This vulnerability is addressed by the following Cisco bug IDs:

  • CSCsd15970 -- MSC crash upon receipt of specific MPLS packets
    This bug only affects CRS-1 and does not affect Cisco 12000 series routers that are running Cisco IOS XR.
    
    
  • CSCsd55531 -- MPLS packet handling problems
    This bug only affects CRS-1 and does not affect Cisco 12000 series routers that are running Cisco IOS XR.
    
    
  • CSCsc77475 -- Line card crash upon receipt of specific MPLS packets
    This bug affects both CRS-1 and Cisco 12000 series routers that are running Cisco IOS XR.
    
    
    

Workarounds

• There is no workaround to mitigate the effects of these vulnerabilities.

Fixed Software

• When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

  In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center ("TAC") or your contracted maintenance provider for assistance.

  Cisco IOS XR Version	SMU ID
  3.2.0	AA01447
  3.2.1	AA01446
  3.2.2	AA01448
  3.2.3 for CRS-1	AA01444
  3.2.3 for PRP	AA01451
  3.2.4	AA01449
  3.2.50	AA01450
  3.3	Cisco IOS XR 3.3 is not vulnerable

Exploitation and Public Announcements

• The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

  This vulnerability was reported to Cisco by a customer.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060419-xr

Revision History

• Revision 1.0

  2006-April-19

  Initial public release.

  Show Less