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Cisco Security Advisory

Cisco IOS Software WebVPN and SSLVPN Vulnerabilities

Advisory ID: cisco-sa-20090325-webvpn

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090325-webvpn

Revision 1.3

For Public Release 2009 March 25 16:00  UTC (GMT)

Related Resources:

View related Alert

Summary

Cisco IOS software contains two vulnerabilities within the Cisco IOS WebVPN or Cisco IOS SSLVPN feature (SSLVPN) that can be remotely exploited without authentication to cause a denial of service condition. Both vulnerabilities affect both Cisco IOS WebVPN and Cisco IOS SSLVPN features:

  1. Crafted HTTPS packet will crash device.
  2. SSLVPN sessions cause a memory leak in the device.

Cisco has released free software updates that address these vulnerabilities.

There are no workarounds that mitigate these vulnerabilities.

This advisory is posted at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090325-webvpn.

Note: The March 25, 2009, Cisco IOS Security Advisory bundled publication includes eight Security Advisories. All of the advisories address vulnerabilities in Cisco IOS Software. Each advisory lists the releases that correct the vulnerability or vulnerabilities in the advisory.

Individual publication links are listed below:

Affected Products

Vulnerable Products

Devices running affected versions of Cisco IOS software are affected if configured with SSLVPN.

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 (c) 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 (c) 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 .

To determine that SSLVPN is enabled on your device, log in to the device and issue the command-line interface (CLI) command "show running-config | include webvpn". If the device returns any output this means that SSLVPN is configured on the device and the device may be vulnerable. Vulnerable configurations vary depending on whether the device is supporting Cisco IOS WebVPN (introduced in Release 12.3(14)T) or Cisco IOS SSLVPNs (introduced in Release 12.4(6)T). The following methods describe how to confirm if the device is vulnerable:

If the output from "show running-config | include webvpn" contains "webvpn enable" then the device is configured with the original Cisco IOS WebVPN. The only way to confirm the device is vulnerable is to examine the output of "show running-config" to confirm that webvpn is enabled via the command "webvpn enable" and that a "ssl trustpoint" has been configured. The following example shows a vulnerable device configured with Cisco IOS WebVPN:

webvpn enable
!
webvpn
 ssl trustpoint TP-self-signed-29742012

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

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

A device that supports the Cisco IOS SSLVPN is not vulnerable if it has no "webvpn gateways" configured or all the configured "webvpn gateways" contain the "no inservice" "webvpn gateway" command.

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 these vulnerabilities.

Details

The Cisco SSLVPN feature provides remote access to enterprise sites by users from anywhere on the Internet. The SSLVPN 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.

The WebVPN Enhancements feature (Cisco IOS SSLVPN), released in Cisco IOS Release 12.4(6)T, obsoletes the commands and configurations originally put forward in Cisco IOS WebVPN.

Further information about Cisco IOS WebVPN is available in the "Cisco IOS Software Release 12.3T WebVPN feature guide" at the following link: http://www.cisco.com/en/US/docs/ios/12_3t/12_3t14/feature/guide/g_sslvpn.html

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

Details regarding these two vulnerabilities in Cisco IOS devices that are running affected versions of system software are:

Crafted HTTPS packet will crash device

A device configured for SSLVPN may reload or hang when it receives a specially crafted HTTPS packet. Completion of the 3-way handshake to the associated TCP port number of the SSLVPN feature is required in order for the vulnerability to be successfully exploited, however authentication is "not" required. The default TCP port number for SSLVPN is 443.

This vulnerability is documented in Cisco bug ID CSCsk62253 (registered customers only) and Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-0626 has been assigned to this vulnerability.

SSLVPN sessions cause a memory leak in the device

A device configured for SSLVPN may leak transmission control blocks (TCBs) when processing an abnormally disconnected SSL session. Continued exploitation may result in the device depleting its memory resources and result in a crash of the device. Authentication is "not" required to exploit this vulnerability.

The memory leak can be detected by running the command "show tcp brief", like in the following example:

Router#show tcp brief
TCB       Local Address      Foreign Address     (state)
468BBDC0  192.168.0.22.443   192.168.0.33.19794   CLOSEWAIT
482D4730  192.168.0.22.443   192.168.0.33.22092   CLOSEWAIT
482779A4  192.168.0.22.443   192.168.0.33.16978   CLOSEWAIT
4693DEBC  192.168.0.22.443   192.168.0.33.21580   CLOSEWAIT
482D3418  192.168.0.22.443   192.168.0.33.17244   CLOSEWAIT
482B8ACC  192.168.0.22.443   192.168.0.33.16564   CLOSEWAIT
46954EB0  192.168.0.22.443   192.168.0.33.19532   CLOSEWAIT
468BA9B8  192.168.0.22.443   192.168.0.33.15781   CLOSEWAIT
482908C4  192.168.0.22.443   192.168.0.33.19275   CLOSEWAIT
4829D66C  192.168.0.22.443   192.168.0.33.19314   CLOSEWAIT
468A2D94  192.168.0.22.443   192.168.0.33.14736   CLOSEWAIT
4688F590  192.168.0.22.443   192.168.0.33.18786   CLOSEWAIT
4693CBA4  192.168.0.22.443   192.168.0.33.12176   CLOSEWAIT
4829ABC4  192.168.0.22.443   192.168.0.33.39629   CLOSEWAIT
4691206C  192.168.0.22.443   192.168.0.33.17818   CLOSEWAIT
46868224  192.168.0.22.443   192.168.0.33.16774   CLOSEWAIT
4832BFAC  192.168.0.22.443   192.168.0.33.39883   CLOSEWAIT
482D10CC  192.168.0.22.443   192.168.0.33.13677   CLOSEWAIT
4829B120  192.168.0.22.443   192.168.0.33.20870   CLOSEWAIT
482862FC  192.168.0.22.443   192.168.0.33.17035   CLOSEWAIT
482EC13C  192.168.0.22.443   192.168.0.33.16053   CLOSEWAIT
482901D8  192.168.0.22.443   192.168.0.33.16200   CLOSEWAIT

In the output above, those Transmission Control Blocks (TCBs) in the state CLOSEWAIT will not go away and represent memory leaks. Please note that only TCP connections with a local TCP port of 443 (the well-known port for HTTPS) are relevant.

This vulnerability is documented in Cisco bug ID CSCsw24700 (registered customers only) and Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-0628 has been assigned to this vulnerability.

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

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 .

CSCsk62253 - Crafted HTTPS packet will crash device.

Calculate the environmental score of CSCsk62253

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

CSCsw24700 - SSLVPN sessions cause a memory leak in the device.

Calculate the environmental score of CSCsw24700

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of any of the two vulnerabilities may result in the device crashing, not accepting any new SSLVPN sessions or a memory leak. Repeated exploitation may result in an extended denial of service (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 Release

Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.0 based releases

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.1 based releases

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.2 based releases

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

12.3

Not Vulnerable

 

12.3B

Not Vulnerable

 

12.3BC

Not Vulnerable

 

12.3BW

Not Vulnerable

 

12.3EU

Not Vulnerable

 

12.3JA

Not Vulnerable

 

12.3JEA

Not Vulnerable

 

12.3JEB

Not Vulnerable

 

12.3JEC

Not Vulnerable

 

12.3JK

Not Vulnerable

 

12.3JL

Not Vulnerable

 

12.3JX

Not Vulnerable

 

12.3T

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3TPC

Not Vulnerable

 

12.3VA

Vulnerable; contact TAC

 

12.3XA

Not Vulnerable

 

12.3XB

Not Vulnerable

 

12.3XC

Not Vulnerable

 

12.3XD

Not Vulnerable

 

12.3XE

Not Vulnerable

 

12.3XF

Not Vulnerable

 

12.3XG

Not Vulnerable

 

12.3XI

Not Vulnerable

 

12.3XJ

Not Vulnerable

 

12.3XK

Not Vulnerable

 

12.3XL

Not Vulnerable

 

12.3XQ

Not Vulnerable

 

12.3XR

Not Vulnerable

 

12.3XS

Not Vulnerable

 

12.3XU

Not Vulnerable

 

12.3XW

Not Vulnerable

 

12.3XX

Not Vulnerable

 

12.3XY

Not Vulnerable

 

12.3XZ

Not Vulnerable

 

12.3YA

Not Vulnerable

 

12.3YD

Not Vulnerable

 

12.3YF

Not Vulnerable

 

12.3YG

Not Vulnerable

 

12.3YH

Not Vulnerable

 

12.3YI

Not Vulnerable

 

12.3YJ

Not Vulnerable

 

12.3YK

Releases prior to 12.3(11)YK3 are vulnerable, release 12.3(11)YK3 and later are not vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3YM

Not Vulnerable

 

12.3YQ

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3YS

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3YT

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3YU

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.3YX

Not Vulnerable

 

12.3YZ

Not Vulnerable

 

12.3ZA

Not Vulnerable

 

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

12.4(18e)

12.4(23a); Available on 05-JUN-2009

12.4(18e)

12.4(23a); Available on 05-JUN-2009

12.4JA

Not Vulnerable

 

12.4JDA

Not Vulnerable

 

12.4JK

Not Vulnerable

 

12.4JL

Not Vulnerable

 

12.4JMA

Not Vulnerable

 

12.4JMB

Not Vulnerable

 

12.4JX

Not Vulnerable

 

12.4MD

Not Vulnerable

 

12.4MR

12.4(16)MR

12.4(19)MR2

12.4SW

Not Vulnerable

 

12.4T

12.4(15)T7

12.4(20)T

12.4(15)T9; Available on 29-APR-2009

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XA

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XB

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XC

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XD

12.4(4)XD12; Available on 27-MAR-2009

12.4(4)XD12; Available on 27-MAR-2009

12.4XE

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XF

Not Vulnerable

 

12.4XG

Not Vulnerable

 

12.4XJ

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XK

Not Vulnerable

 

12.4XL

Not Vulnerable

 

12.4XM

Not Vulnerable

 

12.4XN

Not Vulnerable

 

12.4XP

Vulnerable; contact TAC

 

12.4XQ

Not Vulnerable

 

12.4XR

Not Vulnerable

 

12.4XT

Vulnerable; first fixed in 12.4T

12.4(22)T1

12.4(15)T9; Available on 29-APR-2009

12.4XV

Vulnerable; contact TAC

 

12.4XW

12.4(11)XW10

12.4(11)XW10

12.4XY

12.4(15)XY4

12.4(22)T1

12.4XZ

12.4(15)XZ1

12.4(15)XZ2

12.4YA

Not Vulnerable

 

12.4YB

Not Vulnerable

 

12.4YD

Not Vulnerable

 


Workarounds

There are no workarounds for the vulnerabilities described in this advisory.

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/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 languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory.

These vulnerabilities were discovered 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090325-webvpn

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-teams@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 1.3

2009-June-26

Removed references to the March/09 combined fixed software table.

Revision 1.2

2009-June-1

Updated expected public availability date for release 12.4(23a).

Revision 1.1

2009-May-1

Updated expected public availability date for release 12.4(23a).

Revision 1.0

2009-March-25

Initial 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/web/about/security/psirt/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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