Summary

• The Cisco IOS Software implementation of the network address translation (NAT) feature contains three vulnerabilities when translating IP packets that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.

  Cisco has released software updates that address these vulnerabilities. Workarounds that mitigate these vulnerabilities are not available.

  This advisory is available at the following link:

  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130925-nat

  Note: The September 25, 2013, Cisco IOS Software Security Advisory bundled publication includes eight Cisco Security Advisories. All advisories address vulnerabilities in Cisco IOS Software. 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 2013 bundled publication.

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

  http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep13.html

Affected Products

• These vulnerabilities affect devices that are running vulnerable versions of Cisco IOS Software and have NAT configured.

  Vulnerable Products

  Cisco devices that are running Cisco IOS Software are vulnerable when they are configured for NAT.

  There are two methods to determine whether a device is configured for NAT:

  • Determine whether NAT is active on a device.
  • Determine whether NAT commands are included in the device configuration.

  The preferred method to verify whether NAT is enabled on a Cisco IOS device is to determine whether NAT is active on a device.
  

  Determine Whether NAT is Active on a Device.

  To determine whether NAT has been enabled in the Cisco IOS Software configuration, log in to the device and issue the show ip nat statistics command. If NAT is active, the sections Outside interfaces and Inside interfaces will each include at least one interface. The following example shows a device on which the NAT feature is active:

  Router# show ip nat statistics
  
  Total translations: 2 (0 static, 2 dynamic; 0 extended)
  Outside interfaces: Serial0
  Inside interfaces: Ethernet1
  Hits: 135  Misses: 5
  Expired translations: 2
  Dynamic mappings:
  -- Inside Source
  access-list 1 pool mypool refcount 2
   pool mypool: netmask 255.255.255.0
          start 192.168.10.1 end 192.168.10.254
          type generic, total addresses 14, allocated 2 (14%), misses 0

  Determine Whether NAT Commands are Included in the Device Configuration

  Alternatively, to determine whether NAT has been enabled in the Cisco IOS Software configuration, both the ip nat inside and ip nat outside commands must be present in different interfaces, or in the case of the NAT Virtual Interface, the ip nat enable interface command will be present.

  
  

  Determine the Cisco IOS Software Release

  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

  A Cisco IOS device is not vulnerable if the NAT feature is not configured.

  The following products have been confirmed not vulnerable:

  • Cisco IOS XE Software
  • Cisco IOS XR Software
  • Cisco NX-OS Software
  • Cisco ASA Software

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

Details

• Three vulnerabilities exist in the NAT function of Cisco IOS Software. Two of the vulnerabilities are in the translation of DNS packets and one vulnerability is in the translation of Point-to-Point Tunneling Protocol packets. None of the vulnerabilities require a three-way handshake.

  Cisco IOS Software NAT DNS Vulnerabilities

  Two vulnerabilities exist in the NAT of DNS over TCP packets function of Cisco IOS Software that could allow an unauthenticated remote attacker to reload the affected device. The vulnerabilities are due to improper handling of certain valid DNS TCP streams. An attacker could exploit theses vulnerabilities by sending certain DNS packets on TCP port 53. These DNS vulnerabilities cannot be exploited using UDP port 53 packets nor can they be exploited using IPv6 packets.
  
  The first NAT DNS vulnerability is documented in Cisco bug ID CSCtn53730 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2013-5479.
  
  The second NAT DNS vulnerability is documented in Cisco bug ID CSCuf28733 (registered customers only) and has been assigned CVE ID CVE-2013-5480.
  
  Note: RFC-5966 clarifies that the TCP transport for non-zone-transfer queries is a required part of the full DNS protocol implementation. Disturbing DNS over TCP port 53 could produce unintended consequences.

  Cisco IOS Software NAT PPTP Vulnerability

  A vulnerability exists in the NAT of PPTP packets of Cisco IOS Software that could allow an unauthenticated remote attacker to reload the affected device. The vulnerability is due to the improper handling of the certain valid PPTP packets. An attacker could exploit this vulnerability by sending PPTP packets on TCP port 1723.
  
  NAT for PPTP is performed on TCP port 172 and Generic Routing Encapsulation (GRE) packets on IP protocol 47. The vulnerability can only be triggered using PPTP packets on TCP port 1723.
  
  This vulnerability is documented in Cisco bug ID CSCtq14817 (registered customers only) and has been assigned CVE ID CVE-2013-5481

Workarounds

• There are no workarounds for these vulnerabilities.
  

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 2013 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 2013 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 2013 Bundled Publication
  12.2EX	Not vulnerable	Vulnerable; First fixed in Release 15.0SE
  12.2EY	Not vulnerable	Vulnerable; First fixed in Release 15.2S
  12.2EZ	Not vulnerable	Releases prior to 12.2(60)EZ2 are vulnerable; Releases 12.2(60)EZ2 and later are not vulnerable. First fixed in Release 15.0SE
  12.2IRB	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRC	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRD	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRE	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRF	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2IRG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IRH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IRI	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IXG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2IXH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2MC	Not vulnerable	Vulnerable; First fixed in Release 15.1M
  12.2MRA	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2MRB	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SB	Not vulnerable	12.2(33)SB15
  12.2SCA	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCB	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCC	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCD	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCE	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCF	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCG	Not vulnerable	Vulnerable; First fixed in Release 12.2SCH
  12.2SCH	Not vulnerable	12.2(33)SCH1
  12.2SE	Not vulnerable	12.2(55)SE8
  12.2SEG	Not vulnerable	Vulnerable; First fixed in Release 15.0SE
  12.2SG	Not vulnerable	12.2(53)SG10; available December 2013 *
  12.2SGA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SM	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SQ	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SRA	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRB	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRC	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRD	Not vulnerable	Vulnerable; First fixed in Release 12.2SRE
  12.2SRE	Not vulnerable	12.2(33)SRE9
  12.2STE	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SV	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SVD	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SVE	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SW	Not vulnerable	Vulnerable; First fixed in Release 15.1M
  12.2SXF	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SXH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2SXI	Only Release 12.2(33)SXI7 is vulnerable.	12.2(33)SXI12
  12.2SXJ	Only Release 12.2(33)SXJ1 is vulnerable.	12.2(33)SXJ6
  12.2SY	Vulnerable; First fixed in Release 15.0SY Releases up to and including 12.2(50)SY2 are not vulnerable.	Vulnerable; First fixed in Release 15.0SY
  12.2WO	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2XNA	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNB	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNC	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XND	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNE	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XNF	Please see Cisco IOS XE Software Availability	Please see Cisco IOS XE Software Availability
  12.2XO	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  12.2ZYA	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  Affected 12.3-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Bundled Publication
  There are no affected 12.3 based releases
  Affected 12.4-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Bundled Publication
  There are no affected 12.4 based releases
  Affected 15.0-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Bundled Publication
  15.0EA	Not vulnerable	15.0(2)EA1
  15.0EB	Not vulnerable	Vulnerable; migrate to any release in 15.2E
  15.0EC	Not vulnerable	Vulnerable; migrate to any release in 15.2E
  15.0ED	Not vulnerable	Note: Releases prior to 15.0(2)ED1 are vulnerable; Releases 15.0(2)ED1 and later are not vulnerable.
  15.0EH	Not vulnerable	Not vulnerable
  15.0EJ	Not vulnerable	Not vulnerable
  15.0EX	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0EY	Not vulnerable	15.0(2)EY2
  15.0EZ	Not vulnerable	Only Release 15.0(2)EZ is vulnerable
  15.0M	Only Releases 15.0(1)M6 and 15.0(1)M7 are vulnerable.	Vulnerable; First fixed in Release 15.1M
  15.0MR	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	Vulnerable; First fixed in Release 15.1S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SE	Not vulnerable	15.0(2)SE4
  15.0SG	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SQA	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SQB	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.0SY	15.0(1)SY1	15.0(1)SY5
  15.0XA	Not vulnerable	Vulnerable; First fixed in Release 15.1M
  15.0XO	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory. 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 2013 Bundled Publication
  15.1EY	Not vulnerable	Vulnerable; First fixed in Release 15.2S
  15.1GC	Releases up to and including 15.1(2)GC2 are not vulnerable.	Vulnerable; First fixed in Release 15.1M
  15.1M	15.1(4)M7	15.1(4)M7
  15.1MR	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1MRA	Not vulnerable	15.1(3)MRA2
  15.1S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.1(3)S6 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(2)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; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.1SVD	Not vulnerable	Not vulnerable
  15.1SVE	Not vulnerable	Not vulnerable
  15.1SVF	Not vulnerable	Not vulnerable
  15.1SY	Not vulnerable	15.1(1)SY2; Available on 28-OCT-13 15.1(2)SY
  15.1T	15.1(2)T5 Releases up to and including 15.1(2)T3 are not vulnerable.	Vulnerable; First fixed in Release 15.1M
  15.1XO	Not vulnerable	Not vulnerable
  Affected 15.2-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Bundled Publication
  15.2E	Not vulnerable	Not vulnerable
  15.2GC	Vulnerable; migrate to any release in 15.4T	Vulnerable; migrate to any release in 15.4T
  15.2JA	15.2(4)JA1	15.2(4)JA1
  15.2JAX	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.
  15.2JB	15.2(2)JB2	15.2(2)JB2
  15.2JN	Not vulnerable	Not vulnerable
  15.2M	15.2(4)M4	15.2(4)M4
  15.2S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.2(4)S4 Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.2SA	Not vulnerable	15.2(2)SA
  15.2SNG	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.2SNH	Not vulnerable	Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
  15.2SNI	Not vulnerable	Vulnerable; First fixed in Release 15.3S
  15.2T	15.2(2)T4 15.2(3)T4	15.2(3)T4
  Affected 15.3-Based Releases	First Fixed Release	First Fixed Release for All Advisories in the September 2013 Bundled Publication
  15.3M	Not vulnerable	Not vulnerable
  15.3S	Not vulnerable Cisco IOS XE devices: Please see Cisco IOS XE Software Availability	15.3(2)S2 15.3(3)S Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
  15.3T	15.3(1)T2 15.3(2)T1	15.3(1)T2 15.3(2)T1

  * Cisco Catalyst 4500 Series Switches with Cisco Catalyst 4500 Supervisor Engines 6-E or 6L-E can migrate to Cisco IOS Software Release 15.1SG.

   

   

  Cisco IOS XE Software

  Cisco IOS XE Software is not affected by the vulnerabilities that are disclosed in this document.

   

  Cisco IOS XR Software

  Cisco IOS XR Software is not affected by the vulnerabilities that are disclosed in this document.

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.

  The three vulnerabilities were discovered during  troubleshooting  of TAC customer service requests.

   

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20130925-nat

Revision History

• Revision 1.0

  2013-September-25

  Initial release

  Show Less

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