Cisco Security Advisory: Cisco IOS SSL VPN Vulnerability

22 Sep 2010

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Cisco IOS SSL VPN Vulnerability

Advisory ID: cisco-sa-20100922-sslvpn

http://www.cisco.com/warp/public/707/cisco-sa-20100922-sslvpn.shtml

Revision 1.0

For Public Release 2010 September 22 1600 UTC (GMT)

- ---------------------------------------------------------------------

Summary
=======

Cisco IOS  Software contains a vulnerability when the Cisco IOS SSL
VPN feature is configured with an HTTP redirect. Exploitation could
allow a remote, unauthenticated user to cause a memory leak on the
affected devices, that could result in a memory exhaustion condition
that may cause device reloads, the inability to service new TCP
connections, and other denial of service (DoS) conditions.

Cisco has released free software updates that address this
vulnerability. There is a workaround to mitigate this vulnerability.

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20100922-sslvpn.shtml

Note: The September 22, 2010, Cisco IOS Software Security Advisory
bundled publication includes six Cisco Security Advisories. Five of
the advisories address vulnerabilities in Cisco IOS Software, and one
advisory addresses vulnerabilities in Cisco Unified Communications
Manager. Each advisory lists the releases that correct the
vulnerability or vulnerabilities detailed in the advisory. The table
at the following URL lists releases that correct all Cisco IOS
Software vulnerabilities that have been published on September 22,
2010, or earlier:

http://www.cisco.com/warp/public/707/cisco-sa-20100922-bundle.shtml

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_sep10.html

Affected Products
=================

Vulnerable Products
+------------------

Devices running affected versions of Cisco IOS Software are
vulnerable if configured with SSL VPN and HTTP port redirection.

The following methods may be used to confirm if the device is
configured for Cisco IOS SSL VPNs and is vulnerable:

If the output from show running-config | include webvpn contains
"webvpn gateway <word>" then the device is supporting the Cisco IOS
SSL VPN feature. A device is vulnerable if it has the inservice
command in at least one of the "webvpn gateway" sections and is
configured for HTTP port redirection. The following example shows a
vulnerable device configured with Cisco IOS SSL VPN:

    Router#show running | section webvpn
    webvpn gateway Gateway
     ip address 10.1.1.1 port 443
     http-redirect port 80
     ssl trustpoint Gateway-TP
     inservice
     !
    Router#

A device that supports the Cisco IOS SSL VPN is not vulnerable if
"webvpn gateway" is not configured.

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 12.4(20)T with an installed image name of
C2800NM-ADVSECURITYK9-M:

    Router#show version
    Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2008 by Cisco Systems, Inc.
    Compiled Thu 10-Jul-08 22:00 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 are not affected by this vulnerability:

  * Cisco ASA 5500 Series Adaptive Security Appliances
  * Cisco IOS XR Software
  * Cisco IOS XE Software

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

Details
=======

The Cisco IOS SSL VPN feature provides remote access to enterprise
sites to users anywhere on the Internet. The SSL VPN provides users
with secure access to specific enterprise applications, such as
e-mail and web browsing, without requiring them to have VPN client
software installed on their end-user devices.

Further information about Cisco IOS SSL VPN is available in the
"Cisco IOS Software Release 12.4T SSL VPN feature guide" at the
following link: 
http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/htwebvpn.html leavingcisco.com

A device configured for SSL VPN with HTTP port redirection may leak
transmission control blocks (TCBs) when processing an abnormally
disconnected SSL session. Continued exploitation may cause the device
to deplete memory resources, which could result in device reloads,
the inability to service new TCP connections, and other DoS
conditions. Authentication is not required to exploit this
vulnerability.

A complete TCP 3-way handshake is required to exploit this
vulnerability. The memory leak can be detected by running the command
show tcp brief as shown in the following example:

    Router#show tcp brief
    TCB       Local Address      Foreign Address     (state)
    468BBDC0  192.168.0.22.80   192.168.0.33.19794   CLOSEWAIT
    482D4730  192.168.0.22.80   192.168.0.33.22092   CLOSEWAIT
    482779A4  192.168.0.22.80   192.168.0.33.16978   CLOSEWAIT
    4693DEBC  192.168.0.22.80   192.168.0.33.21580   CLOSEWAIT
    482D3418  192.168.0.22.80   192.168.0.33.17244   CLOSEWAIT
    482B8ACC  192.168.0.22.80   192.168.0.33.16564   CLOSEWAIT
    46954EB0  192.168.0.22.80   192.168.0.33.19532   CLOSEWAIT
    468BA9B8  192.168.0.22.80   192.168.0.33.15781   CLOSEWAIT
    482908C4  192.168.0.22.80   192.168.0.33.19275   CLOSEWAIT
    4829D66C  192.168.0.22.80   192.168.0.33.19314   CLOSEWAIT
    468A2D94  192.168.0.22.80   192.168.0.33.14736   CLOSEWAIT
    4688F590  192.168.0.22.80   192.168.0.33.18786   CLOSEWAIT
    4693CBA4  192.168.0.22.80   192.168.0.33.12176   CLOSEWAIT
    4829ABC4  192.168.0.22.80   192.168.0.33.39629   CLOSEWAIT
    4691206C  192.168.0.22.80   192.168.0.33.17818   CLOSEWAIT
    46868224  192.168.0.22.80   192.168.0.33.16774   CLOSEWAIT
    4832BFAC  192.168.0.22.80   192.168.0.33.39883   CLOSEWAIT
    482D10CC  192.168.0.22.80   192.168.0.33.13677   CLOSEWAIT
    4829B120  192.168.0.22.80   192.168.0.33.20870   CLOSEWAIT
    482862FC  192.168.0.22.80   192.168.0.33.17035   CLOSEWAIT
    482EC13C  192.168.0.22.80   192.168.0.33.16053   CLOSEWAIT
    482901D8  192.168.0.22.80   192.168.0.33.16200   CLOSEWAIT

In the output above, the Transmission Control Blocks (TCBs) in the
state CLOSEWAIT will not transition and represent a memory leak. Note
that only TCP connections with a local TCP port of 80 (the well-known
port for HTTP), as evidenced in the above example by a Local Address
of 192.168.0.22.80, are relevant.

This vulnerability is documented in Cisco bug ID CSCtg21685 
and Common Vulnerabilities and Exposures (CVE) identifier 
CVE-2010-2836 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

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

CSCtg21685 - SSLVPN : TCP remains stuck in closewait state

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 lack of
available memory resources on the affected device, which could affect
new connections to the device such as SSH and Telnet connections.
Depletion of memory resources may also result in failing of routing
protocols and other services.

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 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 For This Advisory column. The First Fixed Release for All
Advisories in the September 2010 Bundle 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.

+-------------------------------------------------------------------+
|   Major    |             Availability of Repaired Releases        |
|  Release   |                                                      |
|------------+------------------------------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 12.0-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|-------------------------------------------------------------------|
| There are no affected 12.0 based releases                         |
|-------------------------------------------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 12.1-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|-------------------------------------------------------------------|
| There are no affected 12.1 based releases                         |
|-------------------------------------------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 12.2-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|-------------------------------------------------------------------|
| There are no affected 12.2 based releases                         |
|-------------------------------------------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 12.3-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|-------------------------------------------------------------------|
| There are no affected 12.3 based releases                         |
|-------------------------------------------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 12.4-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|------------+----------------------+-------------------------------|
| 12.4       | Not Vulnerable       | 12.4(25d)                     |
|------------+----------------------+-------------------------------|
| 12.4GC     | Not Vulnerable       | 12.4(24)GC2                   |
|------------+----------------------+-------------------------------|
| 12.4JA     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JDA    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JDC    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JDD    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JHA    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JHB    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JK     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JL     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JMA    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JMB    | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JX     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4JY     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
| 12.4MD     | Not Vulnerable       | 12.4(24)MD2                   |
|------------+----------------------+-------------------------------|
|            |                      | 12.4(22)MDA4                  |
| 12.4MDA    | Not Vulnerable       |                               |
|            |                      | 12.4(24)MDA1                  |
|------------+----------------------+-------------------------------|
| 12.4MR     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4MRA                       |
|------------+----------------------+-------------------------------|
| 12.4MRA    | Not Vulnerable       | 12.4(20)MRA1                  |
|------------+----------------------+-------------------------------|
| 12.4SW     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            | Releases Prior to    |                               |
|            | 12.4(15)T13 are not  |                               |
|            | vulnerable. First    |                               |
|            | fixed 12.4(15)T14    |                               |
|            |                      | 12.4(15)T14                   |
|            | Releases Prior to    |                               |
| 12.4T      | 12.4(20)T5 are not   | 12.4(20)T6                    |
|            | vulnerable. First    |                               |
|            | fixed 12.4(20)T6     | 12.4(24)T4                    |
|            |                      |                               |
|            | Releases Prior to    |                               |
|            | 12.4(24)T2 are not   |                               |
|            | vulnerable. First    |                               |
|            | fixed 12.4(24)T4     |                               |
|------------+----------------------+-------------------------------|
| 12.4XA     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XB     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XC     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XD     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            |                      | Releases prior to 12.4(6)XE5  |
|            |                      | are vulnerable, release 12.4  |
| 12.4XE     | Not Vulnerable       | (6)XE5 and later are not      |
|            |                      | vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XF     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XG     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XJ     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XK     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4XL     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
| 12.4XM     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4XN     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4XP     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
| 12.4XQ     | Not Vulnerable       | 12.4(15)XQ6; Available on     |
|            |                      | 22-SEP-10                     |
|------------+----------------------+-------------------------------|
|            |                      | 12.4(15)XR9                   |
| 12.4XR     | Not Vulnerable       |                               |
|            |                      | 12.4(22)XR7                   |
|------------+----------------------+-------------------------------|
| 12.4XT     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4XV     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
| 12.4XW     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XY     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4XZ     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
| 12.4YA     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 12.4T                         |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4YB     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
|            |                      | Vulnerable; Contact your      |
|            |                      | support organization per the  |
| 12.4YD     | Not Vulnerable       | instructions in Obtaining     |
|            |                      | Fixed Software section of     |
|            |                      | this advisory                 |
|------------+----------------------+-------------------------------|
| 12.4YE     | Not Vulnerable       | 12.4(24)YE1                   |
|------------+----------------------+-------------------------------|
| 12.4YG     | Not Vulnerable       | 12.4(24)YG3                   |
|------------+----------------------+-------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 15.0-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|------------+----------------------+-------------------------------|
| 15.0M      | 15.0(1)M3            | 15.0(1)M3                     |
|------------+----------------------+-------------------------------|
|            | Cisco 7600 and 10000 | Cisco 7600 and 10000 Series   |
|            | Series routers: Not  | routers: 15.0(1)S1 (available |
|            | vulnerable           | early October 2010)           |
| 15.0S      |                      |                               |
|            | Please see Cisco     | Please see Cisco IOS-XE       |
|            | IOS-XE Software      | Software Availability         |
|            | Availability         |                               |
|------------+----------------------+-------------------------------|
| 15.0XA     | Not Vulnerable       | Vulnerable; first fixed in    |
|            |                      | 15.1T                         |
|------------+----------------------+-------------------------------|
| 15.0XO     | Not Vulnerable       | Not Vulnerable                |
|------------+----------------------+-------------------------------|
|  Affected  | First Fixed Release  |  First Fixed Release for All  |
| 15.1-Based |  for This Advisory   |  Advisories in the September  |
|  Releases  |                      |    2010 Bundle Publication    |
|------------+----------------------+-------------------------------|
|            | 15.1(1)T1            |                               |
| 15.1T      |                      | 15.1(2)T1                     |
|            | 15.1(2)T0a           |                               |
|------------+----------------------+-------------------------------|
|            | Vulnerability        | Vulnerable; first fixed in    |
| 15.1XB     | limited to 15.1(1)   | 15.1T                         |
|            | XB1.                 |                               |
+-------------------------------------------------------------------+

Cisco IOS XE Software
+--------------------

+-------------------------------------------------------------------+
| Cisco IOS |   First Fixed    |    First Fixed Release for All     |
|    XE     | Release for This |  Advisories in the September 2010  |
|  Release  |     Advisory     |         Bundle Publication         |
|-----------+------------------+------------------------------------|
| 2.1.x     | Not Vulnerable   | Not Vulnerable                     |
|-----------+------------------+------------------------------------|
| 2.2.x     | Not Vulnerable   | Not Vulnerable                     |
|-----------+------------------+------------------------------------|
| 2.3.x     | Not Vulnerable   | Not Vulnerable                     |
|-----------+------------------+------------------------------------|
| 2.4.x     | Not Vulnerable   | Not Vulnerable                     |
|-----------+------------------+------------------------------------|
| 2.5.x     | Not Vulnerable   | Vulnerable; migrate to 2.6.2 or    |
|           |                  | later                              |
|-----------+------------------+------------------------------------|
| 2.6.x     | Not Vulnerable   | 2.6.2                              |
|-----------+------------------+------------------------------------|
| 3.1.xS    | Not Vulnerable   | Not Vulnerable                     |
+-------------------------------------------------------------------+

For mapping of Cisco IOS XE Software to Cisco IOS Software releases,
please refer to the Cisco IOS XE 2 and Cisco IOS XE 3S Release Notes.

Cisco IOS XR System Software
+---------------------------

Cisco IOS XR Software is not affected by the vulnerabilities
disclosed in the September 22, 2010, Cisco IOS Software Security
Advisory bundled publication.

Workarounds
===========

Disabling HTTP redirection for SSL VPN connections can be used as a
workaround for this vulnerability. HTTP redirection for SSL VPN
connections is disabled by executing the command no http-redirect
port in webvpn gateway configuration mode.

In addition, manually clearing the hung TCBs with the command clear
tcp tcb * will transition the TCBs into a CLOSED state. After a time
they will clear the CLOSED state and the memory will be released.

Note:  Clearing the TCB will clear both legitimate and hung
connections, including remote connections to the device such as
Telnet and SSH connections.

The Cisco Applied Mitigation Bulletin (AMB) "Identifying and
Mitigating Exploitation of the TCP State Manipulation Denial of
Service Vulnerabilities in Multiple Cisco Products", available at
http://www.cisco.com/warp/public/707/cisco-amb-20090908-tcp24.shtml,
contains two mitigations (EEM scripts and SNMP) that can be used to
detect and clear hung TCP connections.

Embedded Event Manager (EEM)
+---------------------------

A Cisco IOS Embedded Event Manager (EEM) policy that is based on Tool
Command Language (Tcl) can be used on vulnerable Cisco IOS devices to
identify and detect a hung, extended, or indefinite TCP connection
that is caused by this vulnerability. The policy allows
administrators to monitor TCP connections on a Cisco IOS device. When
Cisco IOS EEM detects potential exploitation of this vulnerability,
the policy can trigger a response by sending a syslog message or a
Simple Network Management Protocol (SNMP) trap to clear the TCP
connection. The example policy provided in this document is based on
a Tcl script that monitors and parses the output from two commands at
defined intervals, produces a syslog message when the monitor
threshold reaches its configured value, and can reset the TCP
connection.

The Tcl script is available for download at the "Cisco Beyond:
Embedded Event Manager (EEM) Scripting Community" at the following
link: http://forums.cisco.com/eforum/servlet/EEM?page=eem&fn=script&scriptId=2041
A sample device configuration is provided below.

        !
        !-- Location where the Tcl script will be stored
        !

        event manager directory user policy disk0:/eem

        !
        !-- Define variable and set the monitoring interval
        !-- as an integer (expressed in seconds)
        !

        event manager environment EEM_MONITOR_INTERVAL 60

        !
        !-- Define variable and set the threshold value as
        !-- an integer for the number of retransmissions
        !-- that determine if the TCP connection is hung
        !-- (a recommended value to use is 15)
        !

        event manager environment EEM_MONITOR_THRESHOLD 15

        !
        !-- Define variable and set the value to "yes" to
        !-- enable the clearing of hung TCP connections
        !

        event manager environment EEM_MONITOR_CLEAR yes

        !
        !-- Define variable and set to the TCP connection
        !-- state or states that script will monitor, which
        !-- can be a single state or a space-separated list
        !-- of states
        !

        event manager environment EEM_MONITOR_STATES CLOSEWAIT

        !
        !-- Register the script as a Cisco EEM policy
        !

        event manager policy monitor-sockets.tcl

        !

For more details, refer to the sections "EEM Detecting And Clearing
Hung TCP Connection" and "Identification: Detecting and Clearing Hung
TCP Connection Using SNMP" of this AMB at the following link: 
http://www.cisco.com/warp/public/707/cisco-amb-20090908-tcp24.shtml

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@cisco.com or security-alert@cisco.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@cisco.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 found during the troubleshooting of a customer
service request.

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-20100922-sslvpn.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@cisco.com
  * first-bulletins@lists.first.org
  * bugtraq@securityfocus.com
  * vulnwatch@vulnwatch.org
  * cisco@spot.colorado.edu
  * cisco-nsp@puck.nether.net
  * full-disclosure@lists.grok.org.uk
  * comp.dcom.sys.cisco@newsgate.cisco.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      | 2010-September-22 | 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.h...
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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Cisco Security Advisory: Cisco IOS SSL VPN Vulnerability

Cisco Systems Product Security Incident Response Team