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The U.S. Department of Energy
Computer Incident Advisory Capability
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INFORMATION BULLETIN
Cisco Concentrator RADIUS PAP Authentication Vulnerability
[Cisco Security Advisory - CSCdx82483]
August 8, 2002 14:00 GMT Number M-106
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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.
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VULNERABILITY The risk is HIGH. Sniffed passwords are frequently used to
ASSESSMENT: easily gain access to systems.
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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
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[***** 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
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