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TUCoPS :: Cisco :: m-106.txt

Cisco Concentrator RADIUS PAP Authentication Vulnerability (CIAC M-106)




             __________________________________________________________

                       The U.S. Department of Energy
                   Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___
             __________________________________________________________

                             INFORMATION BULLETIN

           Cisco Concentrator RADIUS PAP Authentication Vulnerability
                     [Cisco Security Advisory - CSCdx82483]

August 8, 2002 14:00 GMT                                          Number M-106
______________________________________________________________________________
PROBLEM:       When a VPN 5000 series concentrator is configured to use a 
               Remote Authentication Dial In User Service (RADIUS) server to 
               authenticate client connections and the challenge type chosen 
               is Password Authentication Protocol (PAP) or Challenge (a 
               hybrid of PAP), the validation retry request sent to the RADIUS 
               server when validation fails the first time does not have the 
               user password field encrypted and so the password is sent as 
               clear text. 
PLATFORM:      All Cisco VPN 5000 series concentrator hardware running 
               software release 6.0.21.0002 (and earlier) and 5.2.23.0003 (and 
               earlier) 
DAMAGE:        Since the password is sent in clear text it can easily be 
               sniffed. 
SOLUTION:      Apply workaround or upgrade software. 
______________________________________________________________________________
VULNERABILITY  The risk is HIGH. Sniffed passwords are frequently used to 
ASSESSMENT:    easily gain access to systems. 
______________________________________________________________________________
LINKS: 
 CIAC BULLETIN:      http://www.ciac.org/ciac/bulletins/m-106l 
 ORIGINAL BULLETIN:                                                           
                     http://www.cisco.com/warp/public/707/vpn5k-radius-pap-vuln-pub.shtml 
______________________________________________________________________________
[***** Start Cisco Security Advisory - CSCdx82483 *****]

Cisco Security Advisory: Cisco VPN 5000 Series Concentrator RADIUS PAP Authentication 
Vulnerability
Revision 1.0
For Public Release 2002 August 07 UTC 1500

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Please provide your feedback on this document.

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Contents 
Summary
Affected Products
Details
Impact
Software Versions and Fixes
Obtaining Fixed Software
Workarounds
Exploitation and Public Announcements
Status of This Notice
Distribution
Revision History
Cisco Security Procedures


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Summary
When a VPN 5000 series concentrator is configured to use a Remote Authentication Dial 
In User Service (RADIUS) server to authenticate client connections and the challenge 
type chosen is Password Authentication Protocol (PAP) or Challenge (a hybrid of PAP), 
the validation retry request sent to the RADIUS server when validation fails the first 
time does not have the user password field encrypted and so the password is sent as 
clear text. A VPN 5000 series concentrator configured to use Challenge-Handshake 
Authentication Protocol (CHAP) to authenticate is not affected by this vulnerability.

This vulnerability is documented as Cisco bug ID CSCdx82483. There are workarounds 
available to mitigate the affects of this vulnerability.

This advisory will be posted at http://www.cisco.com/warp/public/707/vpn5k-radius-pap-
vuln-pub.shtml.

Affected Products
All Cisco VPN 5000 series concentrator hardware running software release 6.0.21.0002 
(and earlier) and 5.2.23.0003 (and earlier) are affected by this vulnerability. This 
series includes models 5001, 5002, and 5008. 

The older IntraPort series concentrator hardware are also affected by this 
vulnerability. This series includes models IntraPort 2, IntraPort 2+, IntraPort 
Enterprise-2 and Enterprise-8, IntraPort Carrier-2, and Carrier-8.

The VPN 3000 series concentrator hardware is not affected.

No other Cisco product is currently known to be affected by this vulnerability.

To determine your software revision, check the revision via the command line interface 
using the show version command.

Details
Cisco VPN 5000 series concentrator hardware running software release 6.0.21.0002 (and 
earlier) and 5.2.23.0003 (and earlier), accepting clients using PAP authentication, 
aggressive mode (AM), or hybrid IKE Extended Authentication (XAUTH) mode, and 
validating against a RADIUS server, are affected by this vulnerability. 

The VPN 5000 series concentrator supports three (3) RADIUS communication types. The [ 
RADIUS ] section keyword ChallengeType can be set to either CHAP, PAP, or Challenge. 
Challenge is a proprietary type of PAP used for Axent Defender authentication. 

In case PAP or Challenge is configured, the remote device sends an authentication 
request to the VPN 5000 series concentrator containing its name and password. The VPN 
5000 series concentrator uses either its internal database or a RADIUS server to 
validate the request and returns an authentication success or failure packet. 

In the event that a RADIUS server is being used, the Access-Request is sent to the 
RADIUS server and the user password is encrypted as specified by the RFC. If the 
Access-Accept packet is not returned in a specific time, due to network or 
configuration problems, the concentrator sends out a retry packet but the user 
password is sent as clear text in this retry packet. 

This vulnerability is documented as Cisco bug ID CSCdx82483, which requires a CCO 
account to view and can be viewed after 2002 August 8 at 1500 UTC.

Impact
During the password validation against a RADIUS server the PAP authentication 
password, in retry packets, is sent in the clear instead of being encrypted. This 
allows the password to be sniffed off the network(s) connecting the VPN 5000 series 
concentrator and the RADIUS server.

Software Versions and Fixes
This vulnerability has been fixed in software release 6.0.21.0003 (and later) and 
5.2.23.0004 (and later).

The procedure to upgrade to the fixed software version is detailed at 
http://www.cisco.com/univercd/cc/td/doc/product/aggr/vpn5000/5000sw/conce60x/5000cfg/s
winst.htm.

Obtaining Fixed Software 
Cisco is offering free software upgrades to address this vulnerability for all 
affected customers. Customers may only install and expect support for the feature sets 
they have purchased.

Customers with service contracts should contact their regular update channels to 
obtain the free software upgrade identified via this advisory. For most customers with 
service contracts, this means that upgrades should be obtained through the Software 
Center on Cisco's worldwide website at http://www.cisco.com/public/sw-center/.

Customers whose Cisco products are provided or maintained through a prior or existing 
agreement with third-party support organizations such as Cisco Partners, authorized 
resellers, or service providers should contact that support organization for 
assistance with obtaining the free software upgrade(s).

Customers who purchased directly from Cisco but who do not hold a Cisco service 
contract, and customers who purchase through third party vendors but are unsuccessful 
at obtaining fixed software through their point of sale, should obtain fixed software 
by contacting the Cisco Technical Assistance Center (TAC) using the contact 
information listed below. In these cases, customers are entitled to obtain an upgrade 
to a later version of the same release or as indicated by the applicable corrected 
software version in the Software Versions and Fixes section (noted above).

Cisco 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 
See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC 
contact information, including special localized telephone numbers and instructions 
and e-mail addresses for use in various languages.

Please have your product serial number available and give the URL of this advisory as 
evidence of your entitlement to a free upgrade.

Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for 
software upgrades.

Workarounds
One workaround is to only use CHAP for authentication by setting ChallengeType = CHAP 
in the [ RADIUS ] section. 

If you have to use PAP for authentication you can set the PrimRetries keyword to a 
value of 1 in the Radius section of the configuration. This would disable any retry 
attempts. Also, if a second (backup) RADIUS server is defined with SecAddress, it must 
be removed as the first attempt to a secondary RADIUS server will have the password in 
the clear. 

For a complete fix please upgrade to a fixed software version of code.

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 reported to PSIRT by a customer.

Status of This Notice: FINAL
This is a final notice. Although Cisco cannot guarantee the accuracy of all statements 
in this advisory, all of the facts have been checked to the best of our ability. Cisco 
does not anticipate issuing updated versions of this advisory unless there is some 
material change in the facts. Should there be a significant change in the facts, Cisco 
may update this advisory.

A stand-alone copy or paraphrase of the text of this security advisory 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 will be posted on Cisco's worldwide website at 
http://www.cisco.com/warp/public/707/vpn5k-radius-pap-vuln-pub.shtml.

In addition to worldwide website posting, a text version of this advisory is clear-
signed with the Cisco PSIRT PGP key having the fingerprint FEB1 1B89 A64B 60BB 4770 
D1CE 93D2 FF06 F236 759C and is posted to the following e-mail and Usenet news 
recipients:

cust-security-announce@cisco.com 
bugtraq@securityfocus.com 
firewalls@lists.gnac.com 
first-teams@first.org (includes CERT/CC) 
cisco@spot.colorado.edu 
cisco-nsp@puck.nether.net 
comp.dcom.sys.cisco 
Various internal Cisco mailing lists 
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 1.0 2002-August-07 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/warp/public/707/sec_incident_response.shtml. 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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This notice is Copyright 2002 by Cisco Systems, Inc. This notice may be redistributed 
freely after the release date given at the top of the text, provided that 
redistributed copies are complete and unmodified, and include all date and version 
information. 


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[***** End Cisco Security Advisory - CSCdx82483 *****]
_______________________________________________________________________________

CIAC wishes to acknowledge the contributions of Cisco for the 
information contained in this bulletin.
_______________________________________________________________________________


CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193 (7x24)
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604
    E-mail:   ciac@ciac.org

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:      http://www.ciac.org/
   Anonymous FTP:       ftp.ciac.org

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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