Summary

• Cisco Internetwork Operating System (IOS) Software is vulnerable to a Denial of Service (DoS) attack from crafted IPv6 packets when the device has been configured to process IPv6 traffic. This vulnerability requires multiple crafted packets to be sent to the device which may result in a reload upon successful exploitation.

  Cisco has made free software available to address this vulnerability.

  There are workarounds available to mitigate the effects.

  This issue is tracked by CERT/CC VU#472582

  This advisory is available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050126-ipv6.

Affected Products

• This section provides details on affected products.

  Vulnerable Products

  Only the Cisco devices running IOS and configured for IPv6 are affected. A router will display all IPv6 enabled interfaces with the show ipv6 interface command.

  An empty output or an error message will be displayed if IPv6 is disabled or unsupported on the system. In this case the system is not vulnerable.

  Sample output of show ipv6 interface command is shown below for a system configured for IPv6.

    Router#show ipv6 interface
    Serial1/0 is up, line protocol is up
      IPv6 is enabled, link-local address is FE80::A8BB:CCFF:FE00:D200
      Global unicast address(es):
        2001:1:33::3, subnet is 2001:1:33::/64 [TENTATIVE]
      Joined group address(es):
        FF02::1
        FF02::1:FF00:3
        FF02::1:FF00:D200
      MTU is 1500 bytes
      ICMP error messages limited to one every 100 milliseconds
      ICMP redirects are enabled
      ND DAD is enabled, number of DAD attempts: 1
      ND reachable time is 30000 milliseconds
    Router#
  

  A router that has IPv6 enabled on a physical or logical interface is vulnerable to this issue even if ipv6 unicast-routing is globally disabled. The show ipv6 interface command can be used to determine whether IPv6 is enabled on any interface.

  Products Confirmed Not Vulnerable

  Products that are not running Cisco IOS are not affected.

  Products running any version of Cisco IOS that do not have IPv6 configured interfaces are not vulnerable.

  No other Cisco products are currently known to be affected by these vulnerabilities.

Details

• IPv6 is the "Internet Protocol Version 6", designed by the Internet Engineering Task Force (IETF) to replace the current version Internet Protocol, IP Version 4 (IPv4).

  A vulnerability exists in the processing of IPv6 packets that can be exploited to cause the reload of a system. Crafted packets received on logical interfaces (that is, tunnels including 6to4 tunnels) as well as physical interfaces can trigger this vulnerability.

  Multiple crafted IPv6 packets need to be sent to exploit this vulnerability. Such crafted packets can be sent remotely.

  This issue is documented in Cisco bug ID CSCed40933 ( registered customers only) .

Workarounds

• The effectiveness of any workaround is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround is the most appropriate for use in the intended network before it is deployed.

  Although it is often difficult to block traffic transiting your network, it is possible to identify traffic which should never be allowed to target your infrastructure devices and block that traffic at the border of your network. Infrastructure access control lists (ACLs) are considered a network security best practice and should be considered as a long-term addition to good network security as well as a workaround for this specific vulnerability. The white paper entitled "Protecting Your Core: Infrastructure Protection Access Control Lists", available at http://www.cisco.com/warp/public/707/iacl.html, presents guidelines and recommended deployment techniques for infrastructure protection ACLs. Exceptions would include any devices which have a legitimate reason to access your infrastructure (for example, BGP peers, DNS servers, and so on). All other traffic must be able to traverse your network without terminating on any of your devices.

Fixed Software

• Major Release	Availability of Repaired Releases
  Affected 12.0-Based Release	Rebuild	Interim	Maintenance
  12.0S	12.0(23)S and before are not vulnerable.
  	12.0(24)S6
  	12.0(25)S3
  	12.0(26)S2
  	12.0(27)S1
  			12.0(28)S
  12.0SX	12.0(25)SX8
  12.0SZ	12.0(27)SZ
  Affected 12.2-Based Release	Rebuild	Interim	Maintenance
  12.2B	12.2(2)B - 12.2(4)B7 Migrate to 12.2(13)T14 or later
  	12.2(4)B8 AND FWD Migrate to 12.3(7)T or later
  12.2BC	Migrate to 12.3(9a)BC
  12.2BX	Migrate to 12.3(7)XI1
  12.2BZ	Migrate to 12.3(7)XI1
  12.2CX	No plan.
  12.2CZ	No plan.
  12.2EW	12.2(18)EW1
  12.2EWA			12.2(20)EWA
  12.2JK	12.2(15)JK2
  12.2MC	Migrate to 12.3(11)T
  12.2S	12.2(14)S9
  	12.2(18)S5
  	12.2(20)S3
  	12.2(22)S1
  			12.2(25)S
  12.2SE	12.2(25)SE
  12.2SU	12.2(14)SU1
  12.2SV	12.2(23)SV
  12.2SW	12.2(23)SW
  12.2SX	Migrate to 12.2(17d)SXB2 or later
  12.2SXA	Migrate to 12.2(17d)SXB1 or later
  12.2SXB	12.2(17d)SXB1
  12.2SXD			12.2(18)SXD
  12.2SY	Migrate to 12.2(17d)SXB2 or later
  12.2SZ	Migrate to 12.2(20)S4
  12.2T	12.2(13)T14
  	12.2(15)T12
  12.2YT	Migrate to 12.2(15)T13 or later
  12.2YU	Migrate to 12.3(4)T6 or later
  12.2YV	Migrate to 12.3(4)T6 or later
  12.2YZ	Migrate to 12.2(20)S4 or later
  12.2ZC	Migrate to 12.3T or later
  12.2ZD	Migrate to 12.3 or later
  12.2ZE	Migrate to 12.3 or later
  12.2ZF	Migrate to 12.3(4)T6 or later
  12.2ZG	Migrate to 12.3(4)T6 or later
  12.2ZH	Migrate to 12.3(4)T6 or later
  12.2ZI	Migrate to 12.2(18)S or later
  12.2ZJ	Migrate to 12.3 or later
  12.2ZL	Migrate to 12.3(7)T or later
  12.2ZN	Migrate to 12.3(2)T6 or later
  12.2ZO	Migrate to 12.2(15)T12 or later
  12.2ZP	Migrate to 12.3(8)XY or later
  Affected 12.3-Based Release	Rebuild	Interim	Maintenance
  12.3	12.3(3f)
  	12.3(5c)
  	12.3(6a)
  			12.3(9)
  12.3BC			12.3(9a)BC
  12.3B	12.3(5a)B2
  12.3BW	Migrate to 12.3(5a)B2 or later
  12.3JA			12.3(2)JA
  12.3T	12.3(2)T6
  	12.3(4)T6
  			12.3(7)T
  12.3XA	Migrate to 12.3(7)T or later
  12.3XB	Migrate to 12.3(8)T or later
  12.3XC	Migrate 12.3(2)XC3 or later
  12.3XD	12.3(4)XD4
  12.3XE	12.3(2)XE1
  12.3XF	Migrate to 12.3(11)T or later
  12.3XG	12.3(4)XG2
  12.3XH	Migrate to 12.3(11)T or later
  12.3XI			12.3(7)XI
  12.3XJ	12.3(7)XJ
  12.3XK	12.3(4)XK1
  12.3XL			12.3(7)XL
  12.3XM			12.3(7)XM
  12.3XN	Migrate to 12.3(14)T or later
  12.3XQ	12.3(4)XQ
  12.3XR			12.3(7)XR
  12.3XS	12.3(7)XS
  12.3XT	12.3(2)XT
  12.3XU	12.3(8)XU
  12.3XX			12.3(8)XX
  12.3XW			12.3(8)XW
  12.3XY			12.3(8)XY
  12.3XZ			12.3(2)XZ
  12.3YA			12.3(8)YA
  12.3YD			12.3(8)YD
  12.3YE			12.3(4)YE
  12.3YF			12.3(11)YF
  12.3YG			12.3(8)YG
  12.3YH			12.3(8)YH

  When considering software upgrades, please also consult http://www.cisco.com/en/US/products/products_security_advisories_listing.html 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) for assistance.

Exploitation and Public Announcements

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

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050126-ipv6

Revision History

• Revision 1.0

  2005-January-26

  Initial public release.

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