[NEWS] Cisco VPN 5000 Series Concentrator RADIUS PAP Authentication Vulnerability
From: support@securiteam.comDate: 08/07/02
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From: support@securiteam.com To: list@securiteam.com Date: Wed, 7 Aug 2002 23:51:59 +0200 (CEST)
The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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Cisco VPN 5000 Series Concentrator RADIUS PAP Authentication Vulnerability
------------------------------------------------------------------------
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.
DETAILS
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 is 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> 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/>
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>
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. In addition, 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.
ADDITIONAL INFORMATION
The information has been provided by <mailto:psirt@cisco.com> Cisco
Systems Product Security Incident Response Team.
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