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Cisco Security Advisory: Cisco VPN 5000 Series Concentrator RADIUS PAP
Authentication Vulnerability
Revision 1.0
For Public Release 2002 August 07 UTC 1500
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/swinst.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: tacat_private
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 "psirtat_private" or
"security-alertat_private" 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-announceat_private
* bugtraqat_private
* firewallsat_private
* first-teamsat_private (includes CERT/CC)
* ciscoat_private
* cisco-nspat_private
* 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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