[apops] Cisco Security Advisory: Cisco IOS Software Firewall Application

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  • Subject: [apops] Cisco Security Advisory: Cisco IOS Software Firewall Application Inspection Control Vulnerability
  • From: Cisco Systems Product Security Incident Response Team <psirt at cisco dot com>
  • Date: Wed, 24 Sep 2008 17:50:00 +0200
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      Cisco Security Advisory: Cisco IOS Software Firewall Application
      Inspection Control Vulnerability
      Advisory ID: cisco-sa-20080924-iosfw
      Revision 1.0
      For Public Release 2008 September 24 1600 UTC (GMT)
      - ---------------------------------------------------------------------
      Cisco IOS software configured for IOS firewall Application Inspection
      Control (AIC) with a HTTP configured application-specific policy are
      vulnerable to a Denial of Service when processing a specific
      malformed HTTP transit packet. Successful exploitation of the
      vulnerability may result in a reload of the affected device.
      Cisco has released free software updates that address this
      A mitigation for this vulnerability is available. See the
      "Workarounds" section for details.
      This advisory is posted at 
      Note: The September 24, 2008 IOS Advisory bundled publication
      includes twelve Security Advisories. Eleven of the advisories address
      vulnerabilities in Cisco's IOS software, and one advisory addresses
      vulnerabilities in Cisco Unified Communications Manager. Each
      Advisory lists the releases that correct the vulnerability described
      in the Advisory. Please reference the following software table to
      find a release that fixes all published IOS software Advisories as of
      September 24th, 2008:
      Individual publication links are listed below:
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-iosips.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-ssl.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-sip.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-cucm.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-vpn.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-mfi.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-ipc.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-ubr.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-multicast.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-sccp.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-l2tp.shtml
      Affected Products
      The HTTP AIC feature was introduced in Cisco IOS Software Release
      12.4(9)T. The software table in this advisory identifies the affected
      Vulnerable Products
      Devices that are running a vulnerable version of Cisco IOS software
      and configured for Cisco IOS firewall AIC for HTTP are affected.
      To determine the software running on a Cisco IOS product, log in to
      the device and issue the show version command-line interface (CLI)
      command to display the system banner. Cisco IOS software will
      identify itself as "Internetwork Operating System Software" or simply
      "IOS." On the next line of output, the image name will be displayed
      between parentheses, followed by "Version" and the Cisco IOS release
      name. Other Cisco devices will not have the show version command, or
      will give different output.
      The following example shows output from a device running Cisco IOS
      image 12.4(15)T2:
          router#show version
          Cisco IOS Software, 1841 Software (C1841-ADVSECURITYK9-M),
             Version 12.4(15)T2, RELEASE SOFTWARE (fc7) Technical Support:
          http://www.cisco.com/techsupport Copyright (c) 1986-2008 by Cisco
          Systems, Inc. Compiled Thu 17-Jan-08 23:12 by prod_rel_team
          !--- Output truncated.
      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 
      The device is vulnerable if the configuration has a Layer 7 class map
      and Layer 7 policy map for HTTP deep packet inspection (DPI), and
      these policies are applied to any firewall zone. To determine whether
      the device is running a vulnerable configuration of Cisco IOS
      firewall AIC for HTTP, log in to the device and issue the CLI command
      show policy-map type inspect zone-pair | section packet inspection.
      If the output contains Policy: http layer7-policymap name , the
      device is vulnerable. The following example shows the response from a
      vulnerable device:
          Router#show policy-map type inspect zone-pair | section packet inspection
                   Deep packet inspection
                      Policy: http layer7-policymap
                      1 packets, 28 bytes
      Products Confirmed Not Vulnerable
      No other Cisco products are currently known to be affected by this
      vulnerability. IOS releases before 12.4(9)T are not affected by this
      issue. Products confirmed not vulnerable include:
        * Cisco PIX
        * Cisco ASA
        * Cisco Firewall Services Module (FWSM)
        * The Virtual Firewall (VFW) application on the multiservice blade
          (MSB) on the Cisco XR 12000 Series Router
      Firewalls are networking devices that control access to an
      organization's network assets. Firewalls are often positioned at the
      entrance points into networks. Cisco IOS software provides a set of
      security features that enable you to configure a simple or elaborate
      firewall policy, according to your particular requirements.
      HTTP uses port 80 by default to transport Internet web services,
      which are commonly used on the network and rarely challenged with
      regard to their legitimacy and conformance to standards. Because port
      80 traffic is typically allowed through the network without being
      challenged, many application developers are leveraging HTTP traffic
      as an alternative transport protocol that will allow their
      application's traffic to travel through or even bypass the firewall.
      When the Cisco IOS Firewall is configured with HTTP AIC, it performs
      packet inspection to detect HTTP connections that are not authorized
      in the scope of the security policy configuration. It also detects
      users who are tunneling applications through port 80. If the packet
      is not in compliance with the HTTP protocol, it will be dropped, the
      connection will be reset, and a syslog message will be generated, as
      Cisco IOS Software that is configured for IOS firewall AIC with an
      HTTP application-specific policy is vulnerable to a denial of service
      condition when it processes a specific malformed HTTP transit packet.
      Successful exploitation of the vulnerability may result in a reload
      of the affected device.
      HTTP runs over TCP. For this vulnerability to be exploited, a full
      three-way handshake between client and server is required before any
      malicious traffic would be processed to result in a device reload.
      Additional information regarding Cisco IOS Firewall AIC with HTTP
      application-specific policy maps is available at 
      This vulnerability is documented in Cisco bug ID CSCsh12480 
      and Common Vulnerabilities and Exposures (CVE) identifier 
      CVE-2008-3812 has been assigned 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
      Cisco has also provided a CVSS calculator to help compute the
      environmental impact for individual networks at
      CSCsh12480 - IOSFW with HTTP AIC may reload on processing crafted
                   HTTP packet
      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
      Successful exploitation of the vulnerability may result in a reload
      of the affected device. Repeated exploitation attempts may result in
      a sustained denial of service attack.
      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
      |  Major Release  |        Availability of Repaired Releases        |
      |    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                    |             |
      | 12.4JA          | 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          | Not Vulnerable                    |             |
      | 12.4SW          | Not Vulnerable                    |             |
      |                 | Releases prior to 12.4(9)T are    |             |
      |                 | not vulnerable. First fixed in:   |             |
      |                 |                                   |             |
      | 12.4T           | 12.4(9)T7                         | 12.4(15)T7  |
      |                 |                                   |             |
      |                 | 12.4(11)T4                        |             |
      |                 |                                   |             |
      |                 | 12.4(15)T                         |             |
      | 12.4XA          | Not Vulnerable                    |             |
      | 12.4XB          | Not Vulnerable                    |             |
      | 12.4XC          | Not Vulnerable                    |             |
      | 12.4XD          | Not Vulnerable                    |             |
      | 12.4XE          | Vulnerable; first fixed in 12.4T  | 12.4(15)T7  |
      | 12.4XF          | Not Vulnerable                    |             |
      | 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          | Not Vulnerable                    |             |
      | 12.4XV          | Vulnerable; contact TAC           |             |
      | 12.4XW          | 12.4(11)XW1                       | 12.4(11)XW9 |
      | 12.4XY          | Not Vulnerable                    |             |
      | 12.4XZ          | Not Vulnerable                    |             |
      | 12.4YA          | Not Vulnerable                    |             |
      There are no known workarounds for this vulnerability. The only known
      action to help counter this vulnerability is to disable AIC HTTP deep
      packet inspection in the affected device's configuration. Disabling
      deep packet HTTP inspection will allow the rest of the firewall
      features to continue to function until a software upgrade can be
      implemented. All other firewall features will continue to perform
      Disabling AIC HTTP Deep Packet Inspection
      To disable AIC HTTP Deep Packet Inspection, remove the linkage
      between policy-map type inspect layer4-policymap and policy-map type
      inspect http layer7-policymap. This example shows an existing
      configuration, followed by how to remove AIC HTTP Deep Packet
          !--- Existing Configuration
          parameter-map type inspect global
          class-map type inspect http match-any layer7-classmap
          class-map type inspect match-any layer4-classmap
           match protocol http
          policy-map type inspect http layer7-policymap
           class type inspect http layer7-classmap
           class class-default
          policy-map type inspect layer4-policymap
           class type inspect layer4-classmap
            inspect global
            service-policy http layer7-policymap
           class class-default
          zone security inside
           description ** Inside Network **
          zone security outside
           description ** Outside Network **
          zone-pair security in2out source inside destination outside
           description ** Zone Pair - inside to outside **
           service-policy type inspect layer4-policymap
      Remove the service-policy from the zone-pair in question:
          Router#configure terminal
          Enter configuration commands, one per line.  End with CNTL/Z.
          Router(config)#zone-pair security in2out source inside destination outside
          Router(config-sec-zone-pair)#no service-policy type inspect layer4-policymap
      Remove the linkage between policy-map type inspect layer4-policymap
      and policy-map type inspect http layer7-policymap:
          Router(config)#policy-map type inspect layer4-policymap
          Router(config-pmap)#class type inspect layer4-classmap
          Router(config-pmap-c)#no service-policy http layer7-policymap
      Reapply the service-policy to the zone-pair in question:
          Router(config)#zone-pair security in2out source inside destination outside
          Router(config-sec-zone-pair)#service-policy type inspect layer4-policymap
      Although not required, for completeness of the configuration the
      policy-map type inspect http layer7-policymap and class-map type
      inspect http match-any layer7-classmap are recommended to be removed.
          Router(config)#no policy-map type inspect http layer7-policymap
          Router(config)#no class-map type inspect http match-any layer7-classmap
      Obtaining Fixed Software
      Cisco has released free software updates that address this
      vulnerability. Prior to deploying software, customers should consult
      their maintenance provider or check the software for feature set
      compatibility and known issues specific to their environment.
      Customers may only install and expect support for the feature sets
      they have purchased. By installing, downloading, accessing or
      otherwise using such software upgrades, customers agree to be bound
      by the terms of Cisco's software license terms found at 
      or as otherwise set forth at Cisco.com Downloads at 
      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/warp/public/687/Directory/DirTAC.shtml
      for additional TAC contact information, including localized telephone
      numbers, and instructions and e-mail addresses for use in various
      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 found by Cisco internal testing.
      Status of this Notice: FINAL
      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.
      This advisory is posted on Cisco's worldwide website at:
      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      | 2008-September-24 | 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 
      This includes instructions for press inquiries regarding Cisco 
      security notices. All Cisco security advisories are available at 
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