[apops] Cisco Security Advisory: Vulnerability in Cisco IOS While Proces

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  • Subject: [apops] Cisco Security Advisory: Vulnerability in Cisco IOS While Processing SSL Packet
  • 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: Vulnerability in Cisco IOS While Processing
      SSL Packet
      Advisory ID: cisco-sa-20080924-ssl
      Revision 1.0
      For Public Release 2008 September 24 1600 UTC (GMT)
      - ---------------------------------------------------------------------
      A Cisco IOS device may crash while processing an SSL packet. This can
      happen during the termination of an SSL-based session. The offending
      packet is not malformed and is normally received as part of the
      packet exchange.
      Cisco has released free software updates that address this
      vulnerability. Aside from disabling affected services, there are no
      available workarounds to mitigate an exploit of this vulnerability.
      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-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-iosfw.shtml
        * http://www.cisco.com/warp/public/707/cisco-sa-20080924-l2tp.shtml
      Affected Products
      Vulnerable Products
      Devices running Cisco IOS and using SSL-based services are
      susceptible to this vulnerability. Some of the services that utilize
      SSL are:
        * HTTP server supporting SSL encryption (HTTPS)
          The following example shows a device that has the standard Cisco
          IOS HTTP server disabled, but the SSL-enabled Cisco IOS HTTP
          server enabled:
              Router#show running-config | include ip http
              no ip http server
              ip http secure-server
        * SSL Virtual Private Network (SSL VPN) also known as AnyConnect
          The following example shows a device that has the SSL VPN feature
              Router#show running-config | include webvpn
              webvpn enable
        * Open Settlement Protocol (OSP) for Packet Telephony feature
          The following example shows a device that has the OSP feature
          enabled and uses HTTPS protocol that is vulnerable:
              Router#show running-config | include url
              url https://<host_ip_address>:443/
      The Cisco IOS Bug Toolkit may not accurately reflect the affected
      releases for this advisory. The affected releases are as follows:
        * 12.4(16)MR, 12.4(16)MR1, 12.4(16)MR2
        * 12.4(17)
      To determine the version of the Cisco IOS software running on a Cisco
      product, log in to the device and issue the show version command to
      display the system banner. Cisco IOS Software will identify itself as
      "Internetwork Operating System Software" or simply "IOS." On the next
      line of output, the image name will be displayed between parentheses,
      followed by "Version" and the IOS release name. Other Cisco devices
      will not have the show version command or will give different output.
          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
      Additional information about Cisco IOS software release naming is
      available at the following link: 
      Products Confirmed Not Vulnerable
      No other Cisco products and Cisco IOS releases are currently known to
      be affected by this vulnerability.
      This vulnerability is triggered during the termination of an SSL
      session. Possession of valid credentials such as a username, password
      or a certificate is not required. SSL protocol uses TCP as a
      transport protocol. The requirement of the complete TCP 3-way
      handshake reduces the probability that this vulnerability will be
      exploited through the use of spoofed IP addresses.
      A device running vulnerable Cisco IOS Software with SSL-based service
      configured will crash while terminating an SSL session.
      This vulnerability is documented in Cisco Bug ID CSCsj85065 and has
      been assigned Common Vulnerabilities and Exposures (CVE) ID 
      Vulnerability Scoring Details
      Cisco has provided scores for the vulnerabilities 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
      CSCsj85065 - Router reload while processing SSL packets
      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
      A successful exploit of this vulnerability may cause a crash of the
      affected device. Repeated exploitation may result in a sustained
      denial of service 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
      |       Major Release       |   Availability of Repaired Releases   |
      |    Affected 12.0-Based    |    First Fixed    |    Recommended    |
      |         Releases          |      Release      |      Release      |
      | There are no affected 12.0 based releases                         |
      |    Affected 12.1-Based    |    First Fixed    |    Recommended    |
      |         Releases          |      Release      |      Release      |
      | There are no affected 12.1 based releases                         |
      |    Affected 12.2-Based    |    First Fixed    |    Recommended    |
      |         Releases          |      Release      |      Release      |
      | There are no affected 12.2 based releases                         |
      |    Affected 12.3-Based    |    First Fixed    |    Recommended    |
      |         Releases          |      Release      |      Release      |
      | There are no affected 12.3 based releases                         |
      |    Affected 12.4-Based    |    First Fixed    |    Recommended    |
      |         Releases          |      Release      |      Release      |
      |                           | 12.4(17a)         |                   |
      | 12.4                      |                   | 12.4(18c)         |
      |                           | 12.4(18)          |                   |
      | 12.4JA                    | Not Vulnerable    |                   |
      | 12.4JK                    | Not Vulnerable    |                   |
      | 12.4JL                    | Not Vulnerable    |                   |
      | 12.4JMA                   | Not Vulnerable    |                   |
      | 12.4JMB                   | Not Vulnerable    |                   |
      | 12.4JMC                   | Not Vulnerable    |                   |
      | 12.4JX                    | Not Vulnerable    |                   |
      | 12.4MD                    | Not Vulnerable    |                   |
      | 12.4MR                    | 12.4(19)MR        | 12.4(19)MR        |
      | 12.4SW                    | Not Vulnerable    |                   |
      | 12.4T                     | 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    |                   |
      | 12.4XT                    | Not Vulnerable    |                   |
      | 12.4XV                    | Not Vulnerable    |                   |
      | 12.4XW                    | Not Vulnerable    |                   |
      | 12.4XY                    | Not Vulnerable    |                   |
      | 12.4XZ                    | Not Vulnerable    |                   |
      To prevent an exploit of a vulnerable device, SSL-based services need
      to be disabled. However, if regular maintenance and operation of the
      device relies on this service, there is no workaround.
      The following command will disable the vulnerable HTTPS service:
          Router(config)#no ip http secure-server
      The following command will disable the vulnerable SSL VPN service:
          Router(config)#no webvpn enable
      The following command will disable the vulnerable OSP service:
          Router(config)#no settlement <n>
      Another option is to revert to HTTP protocol instead using HTTPS. The
      downside of this workaround is that the settlement information will
      be sent over the network unprotected.
      It is possible to mitigate this vulnerability by preventing
      unauthorized hosts from accessing affected devices.
      Control Plane Policing (CoPP)
      Cisco IOS software versions that support Control Plane Policing
      (CoPP) can be configured to help protect the device from attacks that
      target the management and control planes. CoPP is available in Cisco
      IOS release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T.
      In the following CoPP example, the ACL entries that match the exploit
      packets with the permit action will be discarded by the policy-map
      drop function, whereas packets that match a deny action (not shown)
      are not affected by the policy-map drop function:
          !-- Include deny statements up front for any protocols/ports/IP addresses that 
          !-- should not be impacted by CoPP
          !-- Include permit statements for the protocols/ports that will be 
          !-- governed by CoPPaccess-list 100 permit tcp any any eq 443
          !-- 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-SSL-class match access-group 100
          !-- Create a Policy-Map that will be applied to the
          !-- Control-Plane of the device.
          policy-map drop-SSL-policy class drop-SSL-class   drop
          !-- Apply the Policy-Map to the Control-Plane of the
          !-- device.
          control-plane service-policy input drop-SSL-policy
      Note: In the preceding CoPP example, the ACL entries with the permit
      action that match the exploit packets will result in the discarding
      of those packets by the policy-map drop function, whereas packets
      that match the deny action are not affected by the policy-map drop
      Additional information on the configuration and use of the CoPP
      feature is available at the following links: 
      and http://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_feature_guide09186a008052446b.html
      Access Control List (ACL)
      An Access Control List (ACL) can be used to help mitigate attacks
      that target this vulnerability. ACLs can specify that only packets
      from legitimate sources are permitted to reach a device, and all
      others are to be dropped. The following example shows how to allow
      legitimate SSL sessions from trusted sources and deny all other SSL
          access-list 101 permit tcp host <legitimate_host_IP_address> host
             <router_IP_address> eq 443
          access-list 101 deny tcp any any eq 443
      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 
      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.
      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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