Summary

• Cisco IOS Software contains a vulnerability in the Intrusion Prevention System (IPS) feature that could allow an unauthenticated, remote attacker to cause a reload of an affected device if specific Cisco IOS IPS configurations exist.
  
  Cisco has released software updates that address this vulnerability.
  
  Workarounds that mitigate this vulnerability are available.
  
  This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-ios-ips
  

  Note: The September 26, 2012, Cisco IOS Software Security Advisory bundled publication includes nine Cisco Security Advisories. Eight of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses a vulnerability in Cisco Unified Communications Manager. Each Cisco IOS Software Security Advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all Cisco IOS Software vulnerabilities in the September 2012 bundled publication. 

  Individual publication links are in "Cisco Event Response: Semi-Annual Cisco IOS Software Security Advisory Bundled Publication" at the following link:

  http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep12.html

  
  

Affected Products

• 
  

  Vulnerable Products

  Devices configured with Cisco IOS IPS are affected by this vulnerability under certain Cisco IOS IPS configurations when running a vulnerable version of Cisco IOS Software.
  
  A device will have an affected configuration if both of the following two conditions are true:
  

  1. Any of the following categories are enabled in the Cisco IOS IPS configuration:
     • diag2 (in configurations)
     • general_os (in os)
     • general_attack (in attack)
     • general_service (in other_services)
     • tcp (in l2/l3/l4_protocol/ip)
     • udp (in l2/l3/l4_protocol/ip)
     • dns (network_services)
     • advanced (in ios_ips)
     • basic (in ios_ips)
     • past_releases (in releases)

     To determine if any of the preceding categories are enabled, log in to the device and enter the command line interface (CLI) command show ip ips configuration | begin IPS Category CLI Configuration.  If any of the above categories are in the output and have the Enable field value True, then the category is enabled. The following example shows a device with the category basic enabled on the device:

     Router#show ip ips configuration | begin IPS Category CLI Configuration
     IPS Category CLI Configuration:
         Category all:
             Retire: True
             Enable: False
         Category ios_ips basic:
             Retire: False
             Enable: True
         Category other_services:
             Retire: True
             Enable: False

  2. If the four IPS signatures 6054:0, 6054:1, 6062:0, 6062:1 are all not compiled.
  
  To determine if the four signatures are all not compiled log into the device and enter the CLI command show ip ips signatures | include 6054|6062.  If the compiled status column (third column in the example, all of which have the Nr value), shows any value other than Y then the signature is not compiled.  The following example shows a device with all four signatures not compiled on the device:
  

  Router#show ip ips signatures | include 6054|6062
    6062:1     N*  Nr    A      LOW     0     1    0    200   30  FA  N 100 S3
    6062:0     N*  Nr    A      LOW     0     1    0    200   30  FA  N 100 S3
    6054:1     N*  Nr    A      LOW     0     1    0    200   30  FA  N 100 S2
    6054:0     N*  Nr    A      LOW     0     1    0    200   30  FA  N 100 S2

  To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

  The following example identifies a Cisco product that is running Cisco IOS Software Release 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:

  Router> show version 
  Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.0(1)M1, RELEASE SOFTWARE (fc1)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2009 by Cisco Systems, Inc.
  Compiled Wed 02-Dec-09 17:17 by prod_rel_team

  !--- output truncated 

  Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS and NX-OS Software Reference Guide" at http://www.cisco.com/web/about/security/intelligence/ios-ref.html.

  
  

  Products Confirmed Not Vulnerable

  The following products are not affected by this vulnerability:
  

  • Cisco IPS 4200 Series Sensors
  • Cisco IPS 4300 Series Sensors
  • Cisco ASA Advanced Inspection and Prevention Security Services Module
  • Cisco ASA IP Audit for Basic IPS Support
  • Cisco Catalyst 6500 Series Intrusion Detection System
  • Cisco IOS Software Firewall Intrusion Detection System

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

Details

• Cisco IOS Software contains a denial of service vulnerability that could allow an unauthenticated, remote attacker to cause an affected device to reload.
   
  An attacker could exploit this vulnerability by sending legitimate DNS packets through a device with an affected Cisco IOS IPS configuration. An exploit could allow the attacker to cause a reload of the affected device.
  
  
  This vulnerability has been documented in Cisco Bug ID CSCtw55976 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2012-3950.
  

Workarounds

• Either of the following two mitigations will prevent exploitation of the vulnerability against the device: 
  
  Enable DNS Version Request (6054/0 and 6054/1) and DNS Authors Request (6062/0 and 6062/1) signatures on the device
  
  Enabling any of the 6054 or 6062 signatures will prevent exploitation.  The following example shows all four signatures enabled:
  

  Router#configure terminal
  Enter configuration commands, one per line.  End with CNTL/Z.
  Router(config)#ip ips signature-definition
  Router(config-sigdef)#signature 6054 0
  Router(config-sigdef-sig)#status
  Router(config-sigdef-sig-status)#enabled true
  Router(config-sigdef-sig-status)#retired false
  Router(config-sigdef-sig-status)#signature 6054 1
  Router(config-sigdef-sig)#status
  Router(config-sigdef-sig-status)#enabled true
  Router(config-sigdef-sig-status)#retired false
  Router(config-sigdef-sig-status)#signature 6062 0
  Router(config-sigdef-sig)#status
  Router(config-sigdef-sig-status)#enabled true
  Router(config-sigdef-sig-status)#retired false
  Router(config-sigdef-sig-status)#signature 6062 1
  Router(config-sigdef-sig)#status
  Router(config-sigdef-sig-status)#enabled true
  Router(config-sigdef-sig-status)#retired false
  Router(config-sigdef-sig-status)#end
  Do you want to accept these changes? [confirm]

  Disable DNS inspection for Cisco IOS IPS
  
  To configure a Cisco IOS IPS device not to inspect DNS traffic, attach an access list to the IPS name which denies DNS traffic.  The following example shows an ACL attached to the IPS name, which instructs Cisco IOS IPS not to examine DNS packets:
  

  Router#show running-config
  <! output removed for brevity !>
  !
  ip ips name iosips list dont_inspect_dns
  !
  ip access-list extended dont_inspect_dns
   deny   udp any any eq domain
   deny   tcp any any eq domain
   remark <! Include other protocols that are not required to be inspected here !>
   permit ip any any

  Additional information about Tuning, Deploying and Updating Cisco IOS IPS Signature Sets For Multiple-Device Deployments is available at the following link http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6634/white_paper_c11_549300.html

Fixed Software

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

  Cisco IOS Software

  Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the September 2012 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release, where possible.

  The Cisco IOS Software Checker allows customers to search for Cisco Security Advisories that address specific Cisco IOS Software releases. This tool is available on the Cisco Security (SIO) portal at https://sec.cloudapps.cisco.com/security/center/selectIOSVersion.x

  Major Release	Availability of Repaired Releases
  Affected 12.0-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  There are no affected 12.0 based releases
  Affected 12.2-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  There are no affected 12.2 based releases
  Affected 12.3-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  12.3	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3B	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3BC	Not vulnerable	Not vulnerable
  12.3BW	Not vulnerable	Not vulnerable
  12.3JA	Releases prior to 12.3(4)JA2 are vulnerable; Releases 12.3(4)JA2 and later are not vulnerable. Migrate to any release in 12.4JA	Releases prior to 12.3(4)JA2 are vulnerable; Releases 12.3(4)JA2 and later are not vulnerable. Migrate to any release in 12.4JA
  12.3JEA	Not vulnerable	Not vulnerable
  12.3JEB	Not vulnerable	Not vulnerable
  12.3JEC	Not vulnerable	Not vulnerable
  12.3JED	Not vulnerable	Not vulnerable
  12.3JEE	Not vulnerable	Not vulnerable
  12.3JK	Releases prior to 12.3(8)JK1 are vulnerable; Releases 12.3(8)JK1 and later are not vulnerable. Migrate to any release in 12.3T	Releases up to and including 12.3(2)JK3 are not vulnerable. Releases 12.3(8)JK1 and later are not vulnerable. First fixed in Release 12.4
  12.3JL	Not vulnerable	Not vulnerable
  12.3JX	Not vulnerable	Not vulnerable
  12.3T	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3TPC	Not vulnerable	Releases up to and including 12.3(4)TPC11a are not vulnerable.
  12.3VA	Not vulnerable	Not vulnerable
  12.3XA	Not vulnerable	Releases prior to 12.3(2)XA7 are vulnerable; Releases 12.3(2)XA7 and later are not vulnerable. First fixed in Release 12.4
  12.3XB	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.3XC	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XD	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XE	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XF	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.3XG	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XI	Not vulnerable	12.3(7)XI1b
  12.3XJ	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3XK	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XL	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3XQ	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XR	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XU	Not vulnerable	Vulnerable; First fixed in Release 12.4T Releases up to and including 12.3(8)XU1 are not vulnerable.
  12.3XW	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3XX	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XY	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3XZ	Not vulnerable	Vulnerable; First fixed in Release 12.4
  12.3YD	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YF	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YG	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YI	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YJ	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YK	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YM	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YQ	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YS	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YT	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YU	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YX	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.3YZ	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.3ZA	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  Affected 12.4-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  12.4	Not vulnerable	12.4(25g)
  12.4GC	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4JA	Not vulnerable	Not vulnerable
  12.4JAL	Not vulnerable	Not vulnerable
  12.4JAX	Not vulnerable	Not vulnerable
  12.4JAY	Not vulnerable	Not vulnerable
  12.4JDA	Not vulnerable	Not vulnerable
  12.4JDC	Not vulnerable	Not vulnerable
  12.4JDD	Not vulnerable	Not vulnerable
  12.4JDE	Not vulnerable	Not vulnerable
  12.4JHA	Not vulnerable	Not vulnerable
  12.4JHB	Not vulnerable	Not vulnerable
  12.4JHC	Not vulnerable	Not vulnerable
  12.4JK	Not vulnerable	Not vulnerable
  12.4JL	Not vulnerable	Not vulnerable
  12.4JX	Not vulnerable	Not vulnerable
  12.4JY	Not vulnerable	Not vulnerable
  12.4JZ	Not vulnerable	Not vulnerable
  12.4MD	Not vulnerable	12.4(24)MD7
  12.4MDA	Not vulnerable	12.4(24)MDA11 for 7600-SAMI Releases up to and including 12.4(22)MDA6 are not vulnerable.
  12.4MDB	Not vulnerable	12.4(24)MDB10
  12.4MR	Releases prior to 12.4(19)MR1 are vulnerable; Releases 12.4(19)MR1 and later are not vulnerable. Migrate to any release in 12.4MRA	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4MRA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4MRB	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4SW	Not vulnerable	Not vulnerable
  12.4T	12.4(24)T8	12.4(24)T8
  12.4XA	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XB	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XC	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XD	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XE	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XF	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4XG	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XJ	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4XK	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4XL	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4XM	Not vulnerable	Releases up to and including 12.4(15)XM are not vulnerable. Releases 12.4(15)XM3 and later are not vulnerable. First fixed in Release 12.4T
  12.4XN	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4XP	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4XQ	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XR	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XT	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4XV	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4XW	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4XY	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4XZ	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4YA	Vulnerable; First fixed in Release 12.4T	Vulnerable; First fixed in Release 12.4T
  12.4YB	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4YD	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.4YE	Not vulnerable	Vulnerable; First fixed in Release 12.4T
  12.4YG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  Affected 15.0-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  15.0EX	Not vulnerable	Not vulnerable
  15.0EY	Not vulnerable	Not vulnerable
  15.0M	15.0(1)M9	15.0(1)M9
  15.0MR	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.0MRA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.0S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.0(1)S6 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SE	Not vulnerable	15.0(2)SE 15.0(2)SE1; Available on 10-DEC-12
  15.0SG	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.0(2)SG5 15.0(2)SG6; Available on 11-OCT-12 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SQA	Not vulnerable	Not vulnerable
  15.0SY	Not vulnerable	15.0(1)SY2
  15.0XA	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.0XO	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; First fixed in Release 15.0SG Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  Affected 15.1-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  15.1EY	Not vulnerable	15.1(2)EY4
  15.1GC	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.1M	15.1(4)M5	15.1(4)M5
  15.1MR	Not vulnerable	15.1(3)MR
  15.1S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.1(3)S3 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.1SG	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.1(1)SG1 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.1SNG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SNH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SNI	Not vulnerable	Vulnerable; migrate to any release in 15.2SNG
  15.1SV	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1T	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  15.1XB	Vulnerable; First fixed in Release 15.1M	Vulnerable; First fixed in Release 15.1M
  Affected 15.2-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
  15.2GC	Releases prior to 15.2(3)GC are vulnerable; Releases 15.2(3)GC and later are not vulnerable. First fixed in Release 15.2T	Releases prior to 15.2(3)GC are vulnerable; Releases 15.2(3)GC and later are not vulnerable. First fixed in Release 15.2T
  15.2JA	Not vulnerable	Not Vulnerable
  15.2M	Not vulnerable	15.2(4)M
  15.2S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.2(1)S2 15.2(2)S1 15.2(4)S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.2SNG	Not vulnerable	Not vulnerable
  15.2T	15.2(1)T3 15.2(2)T2 15.2(3)T2; Available on 12-OCT-12	15.2(1)T3 15.2(2)T2 15.2(3)T2; Available on 12-OCT-12

  Cisco IOS XE Software

  Cisco IOS XE Software is not affected by the vulnerability that is disclosed in this advisory.
  

  Cisco IOS XR Software

  Cisco IOS XR Software is not affected by the vulnerability that is disclosed in this advisory.

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 when handling customer support requests.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-ios-ips

Revision History

• Revision 1.0

  2012-September-26

  Initial public release

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