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Cisco IOS User Datagram Protocol Delivery Issue For IPv4/IPv6 Dual-stack Routers

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Advisory ID: cisco-sa-20080326-IPv4IPv6

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080326-IPv4IPv6

Revision 1.5

For Public Release 2008 March 26 16:00  UTC (GMT)

Summary

A device running Cisco IOS software that has Internet Protocol version 6 (IPv6) enabled may be subject to a denial of service (DoS) attack. For the device to be affected by this vulnerability the device also has to have certain Internet Protocol version 4 (IPv4) User Datagram Protocol (UDP) services enabled. To exploit this vulnerability an offending IPv6 packet must be targeted to the device. Packets that are routed throughout the router can not trigger this vulnerability. Successful exploitation will prevent the interface from receiving any additional traffic. The only exception is Resource Reservation Protocol (RSVP) service, which if exploited, will cause the device to crash. Only the interface on which the vulnerability was exploited will be affected.

Cisco is providing fixed software to address this issue. There are workarounds available to mitigate the effects of the vulnerability.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080326-IPv4IPv6.

Note: The March 26, 2008 publication includes five Security Advisories. The Advisories all affect Cisco's Internetwork Operating System (IOS). Each Advisory lists the releases that correct the vulnerability described in the Advisory, and the Advisories also detail the releases that correct the vulnerabilities in all five Advisories.

Individual publication links are listed below:

Affected Products

Vulnerable Products

Only Cisco IOS software releases that have IPv6 enabled are affected by this vulnerability. In order to be vulnerable both support for IPv6 protocol and IPv4 UDP-based services must be enabled on the device. The IPv6 is not enabled by default in Cisco IOS software.

To determine the software running on a Cisco IOS product, log in to the device and issue the show version command to display the system banner. Cisco IOS software will identify itself as "Internetwork Operating System Software" or simply "IOS." On the next line of output, the image name will be displayed between parentheses, followed by "Version" and the Cisco IOS software release name. Other Cisco devices will not have the show version command, or will give different output.

The following example shows output from a device running a Cisco IOS image:

Router>show version
Cisco IOS Software, 1841 Software (C1841-ADVSECURITYK9-M), Version 12.4(15)T2, RELEASE SOFTWARE (fc7) 
Technical Support: http://www.cisco.com/techsupport 
Copyright (c) 1986-2008 by Cisco Systems, Inc. 
Compiled Thu 17-Jan-08 23:12 by prod_rel_team

Additional information about Cisco IOS software release naming is available at the following link: http://www.cisco.com/warp/public/620/1.html.

In order for an interface to be vulnerable two conditions must be satisfied:

  1. An interface must have IPv6 enabled.
  2. One or more of the following IPv4 UDP-based services must be enabled:
    TACACS - port 49
    Domain Name System (DNS) server - port 53
    Resource Reservation Protocol (RSVP) - port 1698
    Layer Two Forwarding (L2F)/Layer Two Tunnel Protocol (L2TP) - port 1701
    IP SLA Responder - port 1967
    Media Gateway Control Protocol (MGCP) - port 2427
    Session Initiation Protocol (SIP) - port 5060

No other IPv4 UDP-based services are known to be affected.

How To Verify If IPv6 Is Enabled

IPv6 protocol is enabled on an interface if either or both of the following configuration lines are present in the configuration:

Router#show running-config
interface FastEthernet0/1
 ipv6 address 2001:0DB8:C18:1::/64 eui-64
Router#show running-config
interface FastEthernet0/1
 ipv6 enabled

If any of the interfaces contain either or both of the ipv6 lines then IPv6 is enabled on that particular interface.

How To Verify If IPv4 UDP-based Services Are Enabled

To determine whether device is affected or not, use the show ip sockets command to display all UDP ports device is listening to. In some newer IOS releases the command show ip sockets is obsoleted, and the alternate command show udp can be used instead. The output is identical to the show ip sockets command.

The device is vulnerable if the Local Port column (fifth from the left) in the output of show ip sockets contains any of the port numbers listed in the example below.

Router#show ip sockets
Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
17 192.168.100.1      49 192.168.100.2       49   0   0   11   0 
17 0.0.0.0             0 192.168.100.2       53   0   0  211   0 
17   --listen--          192.168.100.2     1698   0   0    1   0 
17 192.168.100.1    1701 192.168.100.2     1701   1   0 1021   0
17 0.0.0.0             0 192.168.100.2     1967   0   0  211   0 
17 0.0.0.0             0  --any--          2427   0   0  211   0
17 0.0.0.0             0  --any--          5060   0   0  211   0

Products Confirmed Not Vulnerable

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

Any device running Cisco IOS without IPv6 enabled is not vulnerable. Cisco IOS XR and Cisco PIX/ASA are not affected.

Details

To exploit this vulnerability an offending IPv6 packet must be targeted to the device. Packets that are routed throughout the router can not trigger this vulnerability. Successful exploitation of the vulnerability may result in one of the following two conditions:

  1. The device will crash if RSVP service is configured on the interface.
  2. Any other affected IPv4 UDP-based service will prevent the interface from receiving additional traffic. Only the interface on which the vulnerability is exploited will be affected.

This vulnerability is independent of the interface media type. A blocked interface will immediately stop receiving any subsequent packets destined to the device itself until it is unblocked. It is possible to unblock the interface using methods other than a device reload. These methods are described in the Workarounds section. All other interfaces are unaffected and will continue receiving and transmitting packets.

Blocked interface may allow transit traffic to flow for a period of time. Transit traffic may continue to flow until either the respective routing entry or Address Resolution Protocol (ARP) entry expires, whichever event occurs first. Depending on the circumstances the transit traffic can stop flowing through the blocked interface within a few seconds or continue up to four hours (which is the ARP cache default lifetime). After that no further transit traffic will flow through the blocked interface.

No other IPv4 UDP-based services are known to be affected by this vulnerability.

This vulnerability is documented in Cisco Bug ID CSCse56501, and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2008-1153.

Identification Of Vulnerability Exploitation

The show interfaces command can be used to view the input queue size to identify a blocked input interface. A device under attack, but not yet blocked will show the Input queue size increasing without a subsequent decrease. If the current size (in this case, 76) is larger than the maximum size (75), the input queue is blocked. The value of 75 is the default value and it can be changed using the interface command hold-queue X in .

Router#show interfaces FastEthernet 0/1 | include queue
  Input queue: 76/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Output queue: 0/40 (size/max)

The example above shows that the interface FastEthernet0/1 is blocked.

The show ip sockets command can be used to determine which protocol blocks the interface. If In column (sixth from the left) of the output contains any other number than zero (0) that is an indication that packets of that particular protocol are blocking, or starting to block, the interface. The following example shows DNS packets that are beginning to fill the input queue of the interface. The interface is not completely blocked because only 13 packets are in the input queue.

Router#show ip sockets
Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
17 192.168.100.1      49 192.168.100.2       49   0   0   11   0 
17 0.0.0.0             0 192.168.100.2       53  13   0  211   0 
17   --listen--          192.168.100.2     1698   0   0    1   0 
17 192.168.100.1    1701 192.168.100.2     1701   1   0 1021   0
17 0.0.0.0             0 192.168.100.2     1967   0   0  211   0 
17 0.0.0.0             0  --any--          2427   0   0  211   0
17 0.0.0.0             0  --any--          5060   0   0  211   0

The output of the show ip sockets command does not provide information on interfaces. It is possible that packets from multiple protocols may be blocking a single interface. The output of the command must be interpreted with the device's configuration to establish the affected port.

Additional methods that can be used to detect blocked interfaces are described in "Cisco Applied Mitigation Bulletin: User Datagram Protocol Delivery Issue For IPv4/IPv6 Dual-Stack Routers" document available at http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20080326-IPv4IPv6. The method utilizes Embedded Event Manager (EEM) and Applets or an EEM Script.

Vulnerability Scoring Details

Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html.

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss.

UDP delivery issue when IPv4 and IPv6 are bound to the same socket

Calculate the environmental score of CSCse56501

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of the vulnerability can result in one of the following two conditions:

  1. The device will crash if RSVP service is configured on the interface.
  2. Any other affected IPv4 UDP-based service will prevent the interface from receiving additional traffic. Only the interface on which the vulnerability is exploited will be affected.

Software Versions and Fixes

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.

Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.

Major Release

Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

Recommended Release

12.0

Not Vulnerable

12.0DA

Not Vulnerable

12.0DB

Not Vulnerable

12.0DC

Not Vulnerable

12.0S

Vulnerable; contact TAC

12.0SC

Not Vulnerable

12.0SL

Not Vulnerable

12.0SP

Not Vulnerable

12.0ST

Not Vulnerable

12.0SX

Not Vulnerable

12.0SY

Vulnerable; contact TAC

12.0SZ

Vulnerable; contact TAC

12.0T

Not Vulnerable

12.0W

Not Vulnerable

12.0WC

Not Vulnerable

12.0WT

Not Vulnerable

12.0XA

Not Vulnerable

12.0XB

Not Vulnerable

12.0XC

Not Vulnerable

12.0XD

Not Vulnerable

12.0XE

Not Vulnerable

12.0XF

Not Vulnerable

12.0XG

Not Vulnerable

12.0XH

Not Vulnerable

12.0XI

Not Vulnerable

12.0XJ

Not Vulnerable

12.0XK

Not Vulnerable

12.0XL

Not Vulnerable

12.0XM

Not Vulnerable

12.0XN

Not Vulnerable

12.0XQ

Not Vulnerable

12.0XR

Not Vulnerable

12.0XS

Not Vulnerable

12.0XV

Not Vulnerable

12.0XW

Not Vulnerable

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

12.1

Not Vulnerable

12.1AA

Not Vulnerable

12.1AX

Not Vulnerable

12.1AY

Not Vulnerable

12.1AZ

Not Vulnerable

12.1CX

Not Vulnerable

12.1DA

Not Vulnerable

12.1DB

Not Vulnerable

12.1DC

Not Vulnerable

12.1E

Not Vulnerable

12.1EA

Not Vulnerable

12.1EB

Not Vulnerable

12.1EC

Not Vulnerable

12.1EO

Not Vulnerable

12.1EU

Not Vulnerable

12.1EV

Not Vulnerable

12.1EW

Not Vulnerable

12.1EX

Not Vulnerable

12.1EY

Not Vulnerable

12.1EZ

Not Vulnerable

12.1GA

Not Vulnerable

12.1GB

Not Vulnerable

12.1T

Not Vulnerable

12.1XA

Not Vulnerable

12.1XB

Not Vulnerable

12.1XC

Not Vulnerable

12.1XD

Not Vulnerable

12.1XE

Not Vulnerable

12.1XF

Not Vulnerable

12.1XG

Not Vulnerable

12.1XH

Not Vulnerable

12.1XI

Not Vulnerable

12.1XJ

Not Vulnerable

12.1XK

Not Vulnerable

12.1XL

Not Vulnerable

12.1XM

Not Vulnerable

12.1XN

Not Vulnerable

12.1XO

Not Vulnerable

12.1XP

Not Vulnerable

12.1XQ

Not Vulnerable

12.1XR

Not Vulnerable

12.1XS

Not Vulnerable

12.1XT

Not Vulnerable

12.1XU

Vulnerable; first fixed in 12.3

12.3(26)

12.1XV

Vulnerable; first fixed in 12.3

12.3(26)

12.1XW

Not Vulnerable

12.1XX

Not Vulnerable

12.1XY

Not Vulnerable

12.1XZ

Not Vulnerable

12.1YA

Not Vulnerable

12.1YB

Vulnerable; first fixed in 12.3

12.3(26)

12.1YC

Vulnerable; first fixed in 12.3

12.3(26)

12.1YD

Vulnerable; first fixed in 12.3

12.3(26)

12.1YE

Releases prior to 12.1(5)YE6 are vulnerable, release 12.1(5)YE6 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.1YF

Vulnerable; first fixed in 12.3

12.3(26)

12.1YG

Not Vulnerable

12.1YH

Vulnerable; first fixed in 12.3

12.3(26)

12.1YI

Vulnerable; first fixed in 12.3

12.3(26)

12.1YJ

Not Vulnerable

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

12.2

Not Vulnerable

12.2B

Vulnerable; first fixed in 12.4

12.4(18a)

12.2BC

Vulnerable; first fixed in 12.3BC

12.3(23)BC1

12.2BW

Vulnerable; first fixed in 12.3

12.3(26)

12.2BY

Vulnerable; first fixed in 12.4

12.4(18a)

12.2BZ

Vulnerable; first fixed in 12.3XI

12.2CX

Vulnerable; first fixed in 12.3BC

12.3(23)BC1

12.2CY

Vulnerable; first fixed in 12.3BC

12.3(23)BC1

12.2CZ

Vulnerable; contact TAC

12.2DA

Not Vulnerable

12.2DD

Vulnerable; first fixed in 12.4

12.4(18a)

12.2DX

Vulnerable; first fixed in 12.4

12.4(18a)

12.2EU

Vulnerable; first fixed in 12.2SG

12.2(25)EWA13

12.2(31)SGA5

12.2(44)SG

12.2EW

Vulnerable; first fixed in 12.2SG

12.2(25)EWA13

12.2(31)SGA5

12.2(44)SG

12.2EWA

12.2(25)EWA10

12.2(25)EWA11

12.2(25)EWA13

12.2EX

12.2(35)EX1

12.2(37)EX

12.2(40)EX1

12.2EY

12.2(37)EY

12.2EZ

Vulnerable; first fixed in 12.2SEE

12.2FX

Vulnerable; first fixed in 12.2SEE

12.2FY

Vulnerable; first fixed in 12.2SEG

12.2(25)SEG4

12.2FZ

Vulnerable; first fixed in 12.2SE

12.2(44)SE1

12.2IXA

Vulnerable; contact TAC

12.2IXB

Vulnerable; contact TAC

12.2IXC

Vulnerable; contact TAC

12.2IXD

Vulnerable; contact TAC

12.2IXE

Not Vulnerable

12.2JA

Vulnerable; first fixed in 12.3JA

12.2JK

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.2MB

Vulnerable; contact TAC

12.2MC

12.2(15)MC2h

12.2(15)MC2k

12.2S

12.2(14)S18

12.2(18)S13

12.2(20)S14

12.2(25)S13

12.2(25)S15

12.2SB

12.2(28)SB7

12.2(31)SB5

12.2(33)SB; Available on 31-MAR-2008

12.2(31)SB11

12.2SBC

Vulnerable; first fixed in 12.2SB; Available on 31-MAR-2008

12.2(31)SB11

12.2SCA

Not Vulnerable

12.2SE

12.2(35)SE4

12.2(37)SE

12.2(44)SE1

12.2SEA

Vulnerable; first fixed in 12.2SEE

12.2SEB

Vulnerable; first fixed in 12.2SEE

12.2SEC

Vulnerable; first fixed in 12.2SEE

12.2SED

Vulnerable; first fixed in 12.2SEE

12.2SEE

12.2(25)SEE4

12.2SEF

12.2(25)SEF3

12.2(44)SE1

12.2SEG

12.2(25)SEG3

12.2(25)SEG4

12.2SG

12.2(25)SG3

12.2(31)SG3

12.2(37)SG

12.2(44)SG

12.2SGA

12.2(31)SGA2

12.2(31)SGA3

12.2(31)SGA6; Available on 07-APR-2008

12.2(31)SGA5

12.2SL

Not Vulnerable

12.2SM

Vulnerable; contact TAC

12.2SO

Vulnerable; migrate to any release in 12.2SVA

12.2(29)SVD

12.2SRA

12.2(33)SRA4

12.2(33)SRA7

12.2SRB

12.2(33)SRB1

12.2(33)SRB3; Available on 14-APR-08

12.2SRC

Not Vulnerable

12.2SU

Vulnerable; first fixed in 12.4

12.4(18a)

12.2SV

12.2(29b)SV

12.2(29b)SV

12.2SVA

Not Vulnerable

12.2SVC

Not Vulnerable

12.2SVD

Not Vulnerable

12.2SW

Vulnerable; contact TAC

12.2SX

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXA

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXB

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXD

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXE

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXF

12.2(18)SXF10a

12.2(18)SXF12a

12.2(18)SXF9

12.2(18)SXF13

12.2SXH

Not Vulnerable

12.2SY

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SZ

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2T

Vulnerable; first fixed in 12.3

12.3(26)

12.2TPC

12.2(8)TPC10b

12.2UZ

Vulnerable; first fixed in 12.2SB; Available on 31-MAR-2008

12.2(31)SB11

12.2XA

Vulnerable; first fixed in 12.3

12.3(26)

12.2XB

Vulnerable; first fixed in 12.3

12.3(26)

12.2XC

Vulnerable; first fixed in 12.4

12.4(18a)

12.2XD

Vulnerable; first fixed in 12.3

12.3(26)

12.2XE

Vulnerable; first fixed in 12.3

12.3(26)

12.2XF

Vulnerable; first fixed in 12.3BC

12.3(23)BC1

12.2XG

Vulnerable; first fixed in 12.3

12.3(26)

12.2XH

Vulnerable; first fixed in 12.3

12.3(26)

12.2XI

Vulnerable; first fixed in 12.3

12.3(26)

12.2XJ

Vulnerable; first fixed in 12.3

12.3(26)

12.2XK

Vulnerable; first fixed in 12.3

12.3(26)

12.2XL

Vulnerable; first fixed in 12.3

12.3(26)

12.2XM

Vulnerable; first fixed in 12.3

12.3(26)

12.2XN

12.2(33)XN1

12.3(26)

12.2XO

Not Vulnerable

12.2XQ

Vulnerable; first fixed in 12.3

12.3(26)

12.2XR

Vulnerable; first fixed in 12.3

12.3(26)

12.2XS

Not Vulnerable

12.2XT

Vulnerable; first fixed in 12.3

12.3(26)

12.2XU

Vulnerable; first fixed in 12.3

12.3(26)

12.2XV

Vulnerable; first fixed in 12.3

12.3(26)

12.2XW

Vulnerable; first fixed in 12.3

12.3(26)

12.2YA

12.2(4)YA13; Available on 31-MAR-2008

12.3(26)

12.2YB

Vulnerable; first fixed in 12.3

12.3(26)

12.2YC

Vulnerable; first fixed in 12.3

12.3(26)

12.2YD

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YE

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2YF

Vulnerable; first fixed in 12.3

12.3(26)

12.2YG

Vulnerable; first fixed in 12.3

12.3(26)

12.2YH

Vulnerable; first fixed in 12.3

12.3(26)

12.2YJ

Vulnerable; first fixed in 12.3

12.3(26)

12.2YK

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YL

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YM

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YN

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YO

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2YP

Vulnerable; first fixed in 12.3

12.3(26)

12.2YQ

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YR

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YS

Not Vulnerable

12.2YT

Vulnerable; first fixed in 12.3

12.3(26)

12.2YU

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YV

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YW

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YX

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YY

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YZ

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2ZA

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2ZB

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZC

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZD

Vulnerable; contact TAC

12.2ZE

Vulnerable; first fixed in 12.3

12.3(26)

12.2ZF

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZG

Vulnerable; first fixed in 12.3YG

12.4(15)T4

12.4(18a)

12.2ZH

12.2(13)ZH9

12.2(13)ZH11

12.2ZJ

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZL

Vulnerable; first fixed in 12.4

12.4(15)T4

12.4(18a)

12.2ZP

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZU

Vulnerable; migrate to any release in 12.2SXH

12.2(33)SXH2

12.2ZY

Not Vulnerable

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

12.3

12.3(17c)

12.3(18a)

12.3(19a)

12.3(23)

12.3(26)

12.3B

Vulnerable; first fixed in 12.4

12.4(18a)

12.3BC

12.3(17b)BC8

12.3(21a)BC2

12.3(23)BC

12.3(23)BC1

12.3BW

Vulnerable; first fixed in 12.4

12.4(18a)

12.3EU

Not Vulnerable

12.3JA

12.3(11)JA4

12.3(7)JA5

12.3JEA

12.3(8)JEA2

12.3(8)JEA4

12.3JEB

12.3(8)JEB1

12.3(8)JEB2

12.3JEC

Not Vulnerable

12.3JK

12.3(2)JK3

12.3(8)JK

12.3(8)JK1

12.3JL

12.3(2)JL2

12.3(2)JL4

12.3JX

12.3(7)JX9

12.3(7)JX10

12.3T

Vulnerable; first fixed in 12.4

12.4(18a)

12.3TPC

12.3(4)TPC11b

12.3VA

Vulnerable; contact TAC

12.3XA

12.3(2)XA6

12.3(2)XA7; Available on 31-MAR-08

12.3XB

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XC

12.3(2)XC5

12.4(15)T4

12.4(18a)

12.3XD

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XE

12.3(2)XE6; Available on 31-MAR-2008

12.4(15)T4

12.4(18a)

12.3XF

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XG

Vulnerable; first fixed in 12.3YG

12.4(15)T4

12.4(18a)

12.3XH

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XI

12.3(7)XI10

12.3XJ

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3XK

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XQ

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XR

12.3(7)XR7

12.3(7)XR8; Available on 31-MAR-08

12.3XS

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XU

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3XW

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3XY

Vulnerable; first fixed in 12.4

12.4(18a)

12.3YA

Vulnerable; first fixed in 12.4

12.4(15)T4

12.4(18a)

12.3YD

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YF

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3YG

12.3(8)YG6

12.4(15)T4

12.3YH

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YI

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YJ

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YK

12.3(11)YK3

12.4(15)T4

12.3YM

12.3(14)YM10

12.3(14)YM12

12.3YQ

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YS

12.3(11)YS3; Available on 31-MAR-2008

12.4(15)T4

12.3YT

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YU

Vulnerable; first fixed in 12.4XB

12.3YX

12.3(14)YX8

12.3(14)YX11

12.3YZ

12.3(11)YZ2

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

12.4(10c)

12.4(12)

12.4(3h)

12.4(5c)

12.4(7e)

12.4(8d)

12.4(18a)

12.4JA

Not Vulnerable

12.4JK

Not Vulnerable

12.4JMA

Not Vulnerable

12.4JMB

Not Vulnerable

12.4JMC

Not Vulnerable

12.4JX

Not Vulnerable

12.4MD

Not Vulnerable

12.4MR

12.4(12)MR

12.4(16)MR2

12.4SW

12.4(11)SW3

12.4(15)SW

12.4T

12.4(11)T2

12.4(15)T

12.4(2)T6

12.4(4)T8

12.4(6)T8

12.4(9)T3

12.4(15)T4

12.4XA

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.4XB

12.4(2)XB6

12.4XC

12.4(4)XC7

12.4XD

12.4(4)XD7

12.4(4)XD10

12.4XE

12.4(6)XE2

12.4(15)T4

12.4XF

Not Vulnerable

12.4XG

12.4(9)XG2

12.4(9)XG2

12.4XJ

12.4(11)XJ4

12.4(15)T4

12.4XK

Not Vulnerable

12.4XL

Not Vulnerable

12.4XM

Not Vulnerable

12.4XN

Not Vulnerable

12.4XT

12.4(6)XT1

12.4(6)XT2

12.4XV

Not Vulnerable

12.4XW

Not Vulnerable

12.4XY

Not Vulnerable

Workarounds

Interface Access Control List

By deploying an IPv6 Access Control List (ACL) it is possible to prevent offending IPv6 packets reaching vulnerable UDP services. The ACL in the following example will block all IPv6 traffic from reaching vulnerable services.

Router(config)#ipv6 access-list protect_IPv4_services
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq tacacs
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq domain
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq 1698 
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq 1701 
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq 1967 
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq 2427 
Router(config-ipv6-acl)#deny udp any 2001:DB8:1:128::/64 eq 5060

!--- Deny access to link-local address space

Router(config-ipv6-acl)#deny udp any FE80::/10 eq tacacs 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq domain 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq 1698 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq 1701 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq 1967 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq 2427 
Router(config-ipv6-acl)#deny udp any FE80::/10 eq 5060 

!--- Permit/deny all other Layer 3 and Layer 4 traffic       
!--- in accordance with existing security policies and configurations                     
!
!--- Allow all other IPv6 traffic

Router(config-ipv6-acl)#permit ipv6 any 2001:db8:1:128::/64

!
!

Router(config)#interface FastEthernet0/1
Router(config-if)#ipv6 traffic-filter protect_IPv4_services in

Receive Access Control List

Receive Access Lists (rACL) are a feature available on the following hardware models: Cisco 12000 Series, Cisco 7500 Series and Cisco 10720 Router.

By deploying rACL it is possible to prevent offending IPv6 packets from reaching vulnerable UDP services. The rACL in the following example will block all IPv6 traffic from reaching vulnerable services.

Router(config)#ipv6 access-list rACL
Router(config-ipv6-acl)#deny udp any any eq tacacs
Router(config-ipv6-acl)#deny udp any any eq domain
Router(config-ipv6-acl)#deny udp any any eq 1698
Router(config-ipv6-acl)#deny udp any any eq 1701
Router(config-ipv6-acl)#deny udp any any eq 1967
Router(config-ipv6-acl)#deny udp any any eq 2427
Router(config-ipv6-acl)#deny udp any any eq 5060

!--- Allow all other IPv6 traffic

Router(config-ipv6-acl)#permit ipv6 any any
Router(config)#ipv6 receive access-list rACL

Additional Mitigation Techniques

Additional mitigation techniques that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory:

http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20080326-IPv4IPv6

Obtaining Fixed Software

Cisco has released free software updates that address this vulnerability. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml .

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers with Service Contracts

Customers using Third Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix 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 or fix is the most appropriate for use in the intended network before it is deployed.

Customers without Service Contracts

Customers who purchase direct from Cisco but do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

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 encountered in customer networks.

Status of this Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080326-IPv4IPv6

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

  • cust-security-announce@cisco.com
  • first-bulletin@first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk
  • comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.


Revision History

Revision 1.5

2008-June-27

Updated Summary to remove link and verbiage.

Revision 1.4

2008-April-25

Updated CVSS link for CSCse56501.

Revision 1.3

2008-April-14

Link-local address space is added to the iACL example in the Workarounds section

Revision 1.2

2008-April-01

Added workaround using rACL for Cisco routers 12000, 7500 and 10720 series.

Revision 1.1

2008-Mar-29

Updated Software Table for 12.0S, 12.0SY, 12.0SX and 12.0SZ due to new information on advisory ID cisco-sa-20080326-IPv4IPv6, the March 26th advisory on IPv4IPv6 Dual Stack Routers.

Revision 1.0

2008-Mar-26

Initial public release

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.