Cisco IOS IPS Denial of Service Vulnerability

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Updated:May 31, 2014
Document ID:1454798265939145

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Cisco Security Advisory

Cisco IOS IPS Denial of Service Vulnerability

High
Advisory ID:
cisco-sa-20080924-iosips
First Published:
2008 September 24 16:00 GMT
Version 1.1:
Final
Workarounds:
See below
Cisco Bug IDs:
CSCsq13348
CVE-2008-2739
CVSS Score:
Base 7.8, Temporal 6.4Click Icon to Copy Verbose Score
AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
CVE-2008-2739

Summary

Affected Products

  • Vulnerable Products

    Any Cisco IOS device configured with the Cisco IOS IPS feature is vulnerable, regardless if it is configured to use the built-in signatures or an external signature file. Devices using either version 4 or version 5 signatures are affected by this vulnerability.

    The Cisco IOS IPS feature is not enabled by default. The command show ip ips interfaces can be used to determine if the Cisco IOS IPS feature has been configured and applied to any interface on the device, as in the following example:

    Router#show ip ips interfaces
    Interface Configuration
      Interface FastEthernet0/0
        Inbound IPS rule is ios-ips-incoming
        Outgoing IPS rule is not set
      Interface FastEthernet0/1
        Inbound IPS rule is not set
        Outgoing IPS rule is ios-ips-outgoing
Router#

    The output of the show ip ips interfaces command when the Cisco IOS IPS feature has not been configured is dependent on which Cisco IOS release is installed and running on the device. It may be similar to the following example:

    Router#show ip ips interfaces

Router#

    or it may be similar to the following:

    Router#show ip ips interfaces
Interface Configuration
  IPS is not configured on any interface
Router#

    Any version of Cisco IOS prior to the versions which are listed in the Software Versions and Fixes section below is vulnerable.

    To determine the version of the Cisco IOS software running on a Cisco 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 IOS release name. Other Cisco devices will not have the show version command or will give different output.

    The following example identifies a Cisco product running Cisco IOS Software release 12.3(26) with an installed image name of C2500-IS-L:

    Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by cisco Systems, Inc.
Compiled Mon 17-Mar-08 14:39 by dchih

<output truncated>
Router#

    The next example shows a product running Cisco IOS Software release 12.4(20)T with an image name of C1841-ADVENTERPRISEK9-M:

    Router#show version
Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Thu 10-Jul-08 20:25 by prod_rel_team

<output truncated>
Router#

    Additional information on the Cisco IOS release naming conventions can be found on the document entitled "White Paper: Cisco IOS Reference Guide", which is available at http://www.cisco.com/warp/public/620/1.html.

    Products Confirmed Not Vulnerable

    The following Cisco products are confirmed not vulnerable:

    • Cisco IOS devices running the Intrusion Detection System feature
    • Cisco ASA Security Appliances running the Intrusion Detection System feature
    • Cisco PIX 500 Series Security Appliances running the Intrusion Detection System feature
    • Cisco IPS 4200 Sensors
    • Cisco AIP-SSM for ASA 5500 Series Adaptive Security Appliances
    • Cisco Catalyst 6500 Series Intrusion detection System (IDSM-2) Services Module
    • Cisco IPS Advanced Integration Module for Integrated Services Routers

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

Details

  • Cisco IOS Intrusion Prevention System (IPS) is an inline, deep-packet inspection feature that effectively mitigates a wide range of network attacks. A component of the Cisco IOS Integrated Threat Control framework and complemented by Cisco IOS Flexible Packet Matching feature, Cisco IOS IPS provides your network with the intelligence to accurately identify, classify, and stop or block malicious traffic in real time. Additional information on the Cisco IOS IPS feature can be found at http://www.cisco.com/en/US/docs/ios/12_3t/12_3t8/feature/guide/gt_fwids.html.

    Previous to the introduction of the Cisco IOS IPS feature, Cisco IOS provided a similar feature, the Cisco IOS Intrusion Detection System (IDS). The Cisco IOS IDS feature is not affected by this vulnerability. Additional information on the Cisco IOS IDS feature can be found at http://www.cisco.com/en/US/docs/ios/12_0t/12_0t5/feature/guide/ios_ids.html.

    Certain network traffic can trigger IPS signatures on the SERVICE.DNS signature engine which may cause the Cisco IOS device to crash or hang. This may cause a denial of service that results in disruption of network traffic. This vulnerability is documented in Cisco Bug ID CSCsq13348 ( registered customers only) .

    This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-2739.

Workarounds

  • The workaround consists of adding an Access Control List (ACL) to every Cisco IOS IPS policy configured on the device so that traffic destined to ports 53/udp or 53/tcp is not inspected by the Cisco IOS IPS feature. The following ACL would need to be added to the device configuration:

    ! deny inspection of traffic with a destination port of 53/udp
access-list 177 deny   udp any any eq 53
! deny inspection of traffic with a destination port of 53/tcp
access-list 177 deny   tcp any any eq 53
! allow all other traffic to be inspected
access-list 177 permit ip any any

    Every instance of a Cisco IOS IPS policy on the device would then need to be modified in order to reference the previous ACL. In order to determine which Cisco IOS IPS policies are configured on the device, execute the command show running-config | include ip ips name as in the following example:

    Router#show running-config | include ip ips name
ip ips name ios-ips-incoming
ip ips name ios-ips-outgoing
Router#

    In the previous example, two Cisco IOS IPS policies are configured on the device. The following example shows the addition of an ACL to each one of the Cisco IOS IPS policies previously identified:

    Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip ips name ios-ips-incoming list 177
Router(config)#ip ips name ios-ips-outgoing list 177
Router(config)#end
Router#

    As a verification step, the command show ip ips interfaces can be executed again to verify the ACL has been properly attached to each one of the Cisco IOS IPS policies:

    Router#show ip ips interfaces
    Interface Configuration
      Interface FastEthernet0/0
        Inbound IPS rule is ios-ips-incoming
    acl list 177
        Outgoing IPS rule is not set
      Interface FastEthernet0/1
        Inbound IPS rule is not set
        Outgoing IPS rule is ios-ips-outgoing
    acl list 177
Router#

    Note: Disabling or deleting individual or all signatures using the SERVICE.DNS engine of the Cisco IOS IPS feature is not a recommended workaround. The previous workaround is the only Cisco-recommended workaround for this vulnerability.

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.

    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

    There are no affected 12.0 based releases

    Affected 12.1-Based Releases

    First Fixed Release

    Recommended Release

    There are no affected 12.1 based releases

    Affected 12.2-Based Releases

    First Fixed Release

    Recommended Release

    There are no affected 12.2 based releases

    Affected 12.3-Based Releases

    First Fixed Release

    Recommended Release

    12.3

    Not Vulnerable

    12.3B

    Not Vulnerable

    12.3BC

    Not Vulnerable

    12.3BW

    Not Vulnerable

    12.3EU

    Not Vulnerable

    12.3JA

    Not Vulnerable

    12.3JEA

    Not Vulnerable

    12.3JEB

    Not Vulnerable

    12.3JEC

    Not Vulnerable

    12.3JK

    Not Vulnerable

    12.3JL

    Not Vulnerable

    12.3JX

    Not Vulnerable

    12.3T

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3TPC

    Not Vulnerable

    12.3VA

    Not Vulnerable

    12.3XA

    Not Vulnerable

    12.3XB

    Not Vulnerable

    12.3XC

    Not Vulnerable

    12.3XD

    Not Vulnerable

    12.3XE

    Not Vulnerable

    12.3XF

    Not Vulnerable

    12.3XG

    Not Vulnerable

    12.3XI

    Not Vulnerable

    12.3XJ

    Not Vulnerable

    12.3XK

    Not Vulnerable

    12.3XL

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3XQ

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3XR

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3XS

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3XU

    Not Vulnerable

    12.3XW

    Not Vulnerable

    12.3XX

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3XY

    Not Vulnerable

    12.3XZ

    Not Vulnerable

    12.3YA

    Vulnerable; first fixed in 12.4

    12.4(15)T7

    12.4(18c)

    12.3YD

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YF

    Not Vulnerable

    12.3YG

    Releases prior to 12.3(8)YG7 are vulnerable, release 12.3(8)YG7 and later are not vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YH

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YI

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YJ

    Not Vulnerable

    12.3YK

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YM

    12.3(14)YM13; Available on 30-SEP-08

    12.3(14)YM13; Available on 30-SEP-08

    12.3YQ

    Not Vulnerable

    12.3YS

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YT

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.3YU

    Not Vulnerable

    12.3YX

    Not Vulnerable

    12.3YZ

    Vulnerable; contact TAC

    		  

    12.3ZA

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    Affected 12.4-Based Releases

    First Fixed Release

    Recommended Release

    12.4

    12.4(18b)

    12.4(19a)

    12.4(21)

    12.4(18c)

    12.4JA

    Not Vulnerable

    12.4JK

    Not Vulnerable

    12.4JL

    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(19)MR

    12.4(19)MR

    12.4SW

    Not Vulnerable

    12.4T

    12.4(15)T6

    12.4(20)T

    12.4(15)T7

    12.4XA

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XB

    Not Vulnerable

    12.4XC

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XD

    12.4(4)XD11; Available on 26-SEP-08

    12.4(4)XD11; Available on 26-SEP-08

    12.4XE

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XF

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XG

    Not Vulnerable

    12.4XJ

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XK

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XL

    Not Vulnerable

    12.4XM

    Not Vulnerable

    12.4XN

    Not Vulnerable

    12.4XP

    Not Vulnerable

    12.4XQ

    Not Vulnerable

    12.4XT

    Vulnerable; first fixed in 12.4T

    12.4(15)T7

    12.4XV

    Vulnerable; contact TAC

    		  

    12.4XW

    12.4(11)XW9

    12.4(11)XW9

    12.4XY

    12.4(15)XY4

    12.4(15)XY4

    12.4XZ

    12.4(15)XZ2

    12.4(15)XZ2

    12.4YA

    12.4(20)YA1

    12.4(20)YA1

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.

Cisco Security Vulnerability Policy

  • To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

Related to This Advisory

URL

Revision History

  • Revision 1.1

    2009-April-16

    Removed references to the combined software table, as it is now outdated

    Revision 1.0

    2008-September-24

    Initial public release

    Show Less

Cisco Security Vulnerability Policy

  • To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

Related to This Advisory