[apops] Cisco Security Advisory: Cisco IOS Software Network Time Protoco

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  • Subject: [apops] Cisco Security Advisory: Cisco IOS Software Network Time Protocol Packet Vulnerability
  • From: Cisco Systems Product Security Incident Response Team <psirt at cisco dot com>
  • Date: Wed, 23 Sep 2009 12:15:00 -0400
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      Cisco Security Advisory: Cisco IOS Software Network Time Protocol
      Packet Vulnerability
      
      Advisory ID: cisco-sa-20090923-ntp
      
      Revision 1.0
      
      For Public Release 2009 September 23
      
      +---------------------------------------------------------------------
      
      Summary
      =======
      
      Cisco IOS® Software with support for Network Time Protocol (NTP)
      version (v4) contains a vulnerability processing specific NTP packets
      that will result in a reload of the device. This results in a remote
      denial of service (DoS) condition on the affected device.
      
      Cisco has released free software updates that address this
      vulnerability.
      
      Workarounds that mitigate this vulnerability are available.
      
      This advisory is posted at:
      
      http://www.cisco.com/warp/public/707/cisco-sa-20090923-ntp.shtml
      
      Note: The September 23, 2009, Cisco IOS Security Advisory bundled
      publication includes eleven Security Advisories. Ten of the
      advisories address vulnerabilities in Cisco IOS Software, and one
      advisory addresses a vulnerability in Cisco Unified Communications
      Manager. Each advisory lists the releases that correct the
      vulnerability or vulnerabilities detailed in the advisory. The
      following table lists releases that correct all Cisco IOS Software
      vulnerabilities that have been published on September 23, 2009, or
      earlier.
      
      http://www.cisco.com/warp/public/707/cisco-sa-20090923-bundle.shtml
      
      Individual publication links are in "Cisco Event Response: Semiannual
      Cisco IOS Software Advisory Bundled Publication" at the following
      link:
      
      http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep09.html
      
      Affected Products
      =================
      
      Vulnerable Products
      +------------------
      
      Cisco IOS Software devices are vulnerable if they support NTPv4 and
      are configured for NTP operations. NTP is not enabled in Cisco IOS
      Software by default.
      
      To see if a device supports NTPv4, log into the device and via
      configuration mode of the command line interface (CLI), enter the
      command "ntp peer 127.0.0.1 version ?". If the output has the number "4"
      as an option, then the device supports NTPv4. The following example
      identifies a Cisco device that is running a Cisco IOS Software
      release that does support NTPv4:
      
          Router#configure terminal
          Router(config)#ntp peer 127.0.0.1 version ?
            <2-4>  NTP version number
      
      The following example identifies a Cisco device that is running a
      Cisco IOS Software release that does not support NTPv4:
      
          Router(config)#ntp peer 127.0.0.1 version ?
            <1-3>  NTP version number
      
      To see if a device is configured with NTP, log into the device and
      issue the CLI command "show running-config | include ntp". If the
      output returns either of the following commands listed then the
      device is vulnerable:
      
          ntp master <any following commands>
          ntp peer <any following commands>
          ntp server <any following commands>
          ntp broadcast client
          ntp multicast client
      
      The following example identifies a Cisco device that is configured
      with NTP:
      
          router#show running-config | include ntp
          ntp peer 192.168.0.12
      
      The following example identifies a Cisco device that is not
      configured with NTP:
      
          router#show running-config | include ntp
          router#
      
      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 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 ©) 1986-2008 by cisco Systems, Inc.
           Compiled Mon 17-Mar-08 14:39 by dchih
          
           <output truncated>
      
      The following example shows a product that is 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 ©) 1986-2008 by Cisco Systems, Inc.
          Compiled Thu 10-Jul-08 20:25 by prod_rel_team
          
          <output truncated>
      
      Additional information about Cisco IOS Software release naming
      conventions is available in "White Paper: Cisco IOS Reference Guide"
      at the following link:
      
      http://www.cisco.com/warp/public/620/1.html
      
      Products Confirmed Not Vulnerable
      +--------------------------------
      
      The following products and features are not affected by this
      vulnerability:
      
        * Cisco IOS Software devices without support for NTPv4
        * Cisco IOS Software devices configured with only Simple NTP (SNTP)
          feature
        * Cisco IOS XE Software
        * Cisco IOS XR Software
      
      No other Cisco products are currently known to be affected by this
      vulnerability.
      
      Details
      =======
      
      The Network Time Protocol (NTP) is a protocol designed to
      time-synchronize a network of machines. NTP runs over UDP, which in
      turn runs over IP. NTPv3 is documented in RFC1305 leavingcisco.com .
      NTPv4 is a significant revision of the NTP standard, and is the
      current development version, but has not been formalized into an RFC
      at the time of publication of this advisory. NTPv4 is currently
      documented in draft-ietf-ntp-ntpv4-proto-11 leavingcisco.com
      
      When a Cisco IOS Software device supporting NTPv4 receives a specific
      NTP packet it will crash while creating the NTP reply packet. The NTP
      packet can be sent from any remote device, and does not require
      authentication. Cisco IOS devices supporting NTPv4 and configured
      with NTP peer authentication are still vulnerable. The device does
      not have to be explicitly configured for NTPv4 peers. For example a
      device configured with all NTP peers being explicitly labeled as
      version 2 would still be vulnerable, as shown in the following
      example:
      
          Router#show running-config | include ntp
          ntp peer 192.168.0.254 version 2
          ntp peer 192.168.0.1 version 2
          Router#
      
      For further information on the Cisco implementation of NTP, consult
      the configuration guide "Cisco IOS and NX-OS Software - Performing
      Basic System Management" at the following link:
      
      http://www.cisco.com/en/US/docs/ios/netmgmt/configuration/guide/nm_basic_sys_manage.html#wp1001170
      
      This vulnerability is documented in the following Cisco Bug IDs: 
      CSCsu24505 and CSCsv75948 and has been assigned the Common Vulnerabilities
      and Exposures (CVE) identifier CVE-2009-2869. Both Cisco bug IDs are
      required for a full fix to this vulnerability.
      
      Vulnerability Scoring Details
      =============================
      
      Cisco has provided scores for the vulnerability 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
      
      CSCsu24505, CSCsv75948 - Cisco IOS Software NTP Packet Vulnerability
      
      CVSS Base Score - 7.8
      
      Access Vector           - Network
      Access Complexity       - Low
      Authentication          - None
      Confidentiality Impact  - None
      Integrity Impact        - None
      Availability Impact     - Complete
      
      CVSS Temporal Score - 6.4
      
      Exploitability          - Functional
      Remediation Level       - Official-Fix
      Report Confidence       - Confirmed
      
      Impact
      ======
      
      Successful exploitation of the vulnerability may result in a reload
      of the device. The vulnerability could be repeatedly exploited to
      cause an extended DoS condition.
      
      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    |          Availability of Repaired Releases           |
      |  Release   |                                                      |
      |------------+------------------------------------------------------|
      |  Affected  |                                       | Recommended  |
      | 12.0-Based |          First Fixed Release          |   Release    |
      |  Releases  |                                       |              |
      |-------------------------------------------------------------------|
      | There are no affected 12.0 based releases                         |
      |-------------------------------------------------------------------|
      |  Affected  |                                       | Recommended  |
      | 12.1-Based |          First Fixed Release          |   Release    |
      |  Releases  |                                       |              |
      |-------------------------------------------------------------------|
      | There are no affected 12.1 based releases                         |
      |-------------------------------------------------------------------|
      |  Affected  |                                       | Recommended  |
      | 12.2-Based |          First Fixed Release          |   Release    |
      |  Releases  |                                       |              |
      |-------------------------------------------------------------------|
      | There are no affected 12.2 based releases                         |
      |-------------------------------------------------------------------|
      |  Affected  |                                       | Recommended  |
      | 12.3-Based |          First Fixed Release          |   Release    |
      |  Releases  |                                       |              |
      |-------------------------------------------------------------------|
      | There are no affected 12.3 based releases                         |
      |-------------------------------------------------------------------|
      |  Affected  |                                       | Recommended  |
      | 12.4-Based |          First Fixed Release          |   Release    |
      |  Releases  |                                       |              |
      |------------+---------------------------------------+--------------|
      | 12.4       | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4GC     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JA     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JDA    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JDC    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JDD    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JK     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JL     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JMA    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JMB    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4JX     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      |            | Releases prior to 12.4(22)MD are not  |              |
      | 12.4MD     | vulnerable, vulnerability was first   | 12.4(22)MD1  |
      |            | introduced in 12.4(22)MD, first fixed |              |
      |            | in 12.4(22)MD1.                       |              |
      |------------+---------------------------------------+--------------|
      | 12.4MDA    | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4MR     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4SW     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      |            | Releases prior to 12.4(20)T are not   |              |
      |            | vulnerable.                           |              |
      |            |                                       | 12.4(20)T4   |
      |            | 12.4(20)T and 12.4(20)T1 are          |              |
      |            | vulnerable, vulnerability is first    | 12.4(22)T3   |
      | 12.4T      | fixed in 12.4(20)T2.                  |              |
      |            |                                       | 12.4(24)T2;  |
      |            | 12.4(22)T is vulnerable,              | Available on |
      |            | vulnerability is first fixed in 12.4  | 23-OCT-2009  |
      |            | (22)T1                                |              |
      |            |                                       |              |
      |            | 12.4(24)T is not vulnerable.          |              |
      |------------+---------------------------------------+--------------|
      | 12.4XA     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XB     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XC     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XD     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XE     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XF     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XG     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XJ     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XK     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XL     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XM     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XN     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XP     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XQ     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XR     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XT     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XV     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XW     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4XY     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      |            |                                       | 12.4(20)T4   |
      |            |                                       |              |
      |            |                                       | 12.4(22)T3   |
      | 12.4XZ     | Vulnerable; first fixed in 12.4T      |              |
      |            |                                       | 12.4(24)T2;  |
      |            |                                       | Available on |
      |            |                                       | 23-OCT-2009  |
      |------------+---------------------------------------+--------------|
      |            |                                       | 12.4(20)T4   |
      |            |                                       |              |
      |            |                                       | 12.4(22)T3   |
      | 12.4YA     | Vulnerable; first fixed in 12.4T      |              |
      |            |                                       | 12.4(24)T2;  |
      |            |                                       | Available on |
      |            |                                       | 23-OCT-2009  |
      |------------+---------------------------------------+--------------|
      | 12.4YB     | Not Vulnerable                        |              |
      |------------+---------------------------------------+--------------|
      | 12.4YD     | 12.4(22)YD1                           | 12.4(22)YD1  |
      |------------+---------------------------------------+--------------|
      | 12.4YE     | 12.4(22)YE1                           | 12.4(22)YE1  |
      +-------------------------------------------------------------------+
      
      Workarounds
      ===========
      
      There are no workarounds other than disabling NTP on the device. The
      following mitigations have been identified for this vulnerability;
      only packets destined for any configured IP address on the device can
      exploit this vulnerability. Transit traffic will not exploit this
      vulnerability.
      
      Note: NTP peer authentication is not a workaround and is still a
      vulnerable configuration.
      
      NTP Access Group
      +---------------
      
      Warning: Because the feature in this vulnerability utilizes
      UDP as a transport, it is possible to spoof the sender's IP address,
      which may defeat access control lists (ACLs) that permit
      communication to these ports from trusted IP addresses. Unicast
      Reverse Path Forwarding (Unicast RPF) should be considered to be used
      in conjunction to offer a better mitigation solution.
      
          
          !--- Configure trusted peers for allowed access
          
          
          access-list 1 permit 171.70.173.55
          
          
          !--- Apply ACE to the NTP configuration
          
          
          ntp access-group 1
      
      For additional information on NTP access control groups, consult the
      document titled "Performing Basic System Management" at the following
      link:
      
      http://www.cisco.com/en/US/docs/ios/netmgmt/configuration/guide/nm_basic_sys_manage.html#wp1034942
      
      Infrastructure Access Control Lists
      +----------------------------------
      
      warning Warning: Because the feature in this vulnerability utilizes
      UDP as a transport, it is possible to spoof the sender's IP address,
      which may defeat ACLs that permit communication to these ports from
      trusted IP addresses. Unicast RPF should be considered to be used in
      conjunction to offer a better mitigation solution.
      
      Although it is often difficult to block traffic that transits a
      network, it is possible to identify traffic that should never be
      allowed to target infrastructure devices and block that traffic at
      the border of networks. Infrastructure ACLs (iACLs) are 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 iACL example below should be included as
      part of the deployed infrastructure access-list, which will help
      protect all devices with IP addresses in the infrastructure IP
      address range:
      
          
          !---
          !--- Feature: Network Time Protocol (NTP)
          !---
          
          
          access-list 150 permit udp TRUSTED_SOURCE_ADDRESSES WILDCARD 
              INFRASTRUCTURE_ADDRESSES WILDCARD eq 123
          
          
          !--- Note: If the router is acting as a NTP broadcast client
          !---   via the interface command "ntp broadcast client"
          !---   then broadcast and directed broadcasts must be 
          !---   filtered as well.  The following example covers
          !---   an infrastructure address space of 192.168.0.X
          
          
          access-list 150 permit udp TRUSTED_SOURCE_ADDRESSES WILDCARD 
              host 192.168.0.255 eq ntp
          access-list 150 permit udp TRUSTED_SOURCE_ADDRESSES WILDCARD 
              host 255.255.255.255 eq ntp
          
          
          !--- Note: If the router is acting as a NTP multicast client
          !---   via the interface command "ntp multicast client"
          !---   then multicast IP packets to the mutlicast group must
          !---   be filtered as well.  The following example covers
          !---   a NTP multicast group of 239.0.0.1 (Default is
          !---   224.0.1.1)
          
          
          access-list 150 permit udp TRUSTED_SOURCE_ADDRESSES WILDCARD 
              host 239.0.0.1 eq ntp
          
          
          !--- Deny NTP traffic from all other sources destined
          !--- to infrastructure addresses.
          
          
          access-list 150 deny udp any 
              INFRASTRUCTURE_ADDRESSES WILDCARD eq 123
          
          
          !--- Permit/deny all other Layer 3 and Layer 4 traffic in
          !--- accordance with existing security policies and
          !--- configurations.  Permit all other traffic to transit the
          !--- device.
          
          
          access-list 150 permit ip any any
          
          
          !--- Apply access-list to all interfaces (only one example
          !--- shown)
           
          
          interface fastEthernet 2/0
           ip access-group 150 in
      
      The white paper entitled "Protecting Your Core: Infrastructure
      Protection Access Control Lists" presents guidelines and recommended
      deployment techniques for infrastructure protection access lists and
      is available at the following link:
      
      http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml
      
      Control Plane Policing
      +---------------------
      
      Warning: Because the feature in this vulnerability utilizes UDP as a
      transport, it is possible to spoof the sender's IP address, which may
      defeat ACLs that permit communication to these ports from trusted IP
      addresses. Unicast RPF should be considered to be used in conjunction
      to offer a better mitigation solution.
      
      Control Plane Policing (CoPP) can be used to block untrusted UDP
      traffic to the device. Cisco IOS software releases 12.0S, 12.2SX,
      12.2S, 12.3T, 12.4, and 12.4T support the CoPP feature. CoPP can be
      configured on a device to help protect the management and control
      planes and minimize the risk and effectiveness of direct
      infrastructure attacks by explicitly permitting only authorized
      traffic that is sent to infrastructure devices in accordance with
      existing security policies and configurations. The CoPP example below
      should be included as part of the deployed CoPP, which will help
      protect all devices with IP addresses in the infrastructure IP
      address range.
      
          
          !--- Feature: Network Time Protocol (NTP)
          
          
          access-list 150 deny udp TRUSTED_SOURCE_ADDRESSES WILDCARD
               any eq 123
          
          
          !--- Deny NTP traffic from all other sources destined
          !--- to the device control plane.
          
          
          access-list 150 permit udp any any eq 123
          
          
          !--- Permit (Police or Drop)/Deny (Allow) all other Layer3 and 
          !--- Layer4 traffic in accordance with existing security policies
          !--- and configurations for traffic that is authorized to be sent
          !--- to infrastructure devices
          !--- Create a Class-Map for traffic to be policed by
          !--- the CoPP feature
          
          
          class-map match-all drop-udp-class
           match access-group 150
          
          
          !--- Create a Policy-Map that will be applied to the
          !--- Control-Plane of the device.
          
          
          policy-map drop-udp-traffic
           class drop-udp-class
            drop
          
          
          !--- Apply the Policy-Map to the 
          !--- Control-Plane of the device
          
          
          control-plane
           service-policy input drop-udp-traffic
      
      In the above CoPP example, the access control list entries (ACEs)
      that match the potential exploit packets with the "permit" action
      result in these packets being discarded by the policy-map "drop"
      function, while packets that match the "deny" action (not shown) are
      not affected by the policy-map drop function. Please note that the
      policy-map syntax is different in the 12.2S and 12.0S Cisco IOS
      Software trains:
      
          policy-map drop-udp-traffic
          class drop-udp-class
          police 32000 1500 1500 conform-action drop exceed-action drop
      
      Additional information on the configuration and use of the CoPP
      feature can be found in the documents, "Control Plane Policing
      Implementation Best Practices" and "Cisco IOS Software Releases 12.2
      S - Control Plane Policing" at the following links:
      
      http://www.cisco.com/web/about/security/intelligence/coppwp_gs.html
      
      and
      
      http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html
      
      Obtaining Fixed Software
      ========================
      
      Cisco has released free software updates that address these
      vulnerabilities. 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 at cisco dot com or security-alert at cisco dot 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 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 at cisco dot 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/en/US/support/tsd_cisco_worldwide_contacts.html
      
      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 discovered by Cisco when handling customer
      support calls.
      
      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://www.cisco.com/warp/public/707/cisco-sa-20090923-ntp.shtml
      
      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 at cisco dot com
        * first-bulletins at lists dot first dot org
        * bugtraq at securityfocus dot com
        * vulnwatch at vulnwatch dot org
        * cisco at spot dot colorado dot edu
        * cisco-nsp at puck dot nether dot net
        * full-disclosure at lists.grok dot org dot uk
        * comp.dcom.sys.cisco at newsgate dot cisco dot 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 |                   | Initial |
      | 1.0      | 2009-September-23 | 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
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