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Home » Hacking News » CA-2002-06-Vulnerabilities in Various Implementations of the RADIUS Protocol

CA-2002-06-Vulnerabilities in Various Implementations of the RADIUS Protocol

by Nikola Strahija on March 5th, 2002 Remote Authentication Dial In User Service (RADIUS) servers are used for authentication, authorization and accounting for terminals that speak the RADIUS protocol. Multiple vulnerabilities have been discovered in several implementations of the RADIUS protocol.

Systems Affected

Systems running any of the following RADIUS implementations:

* Ascend RADIUS versions 1.16 and prior
* Cistron RADIUS versions 1.6.5 and prior
* FreeRADIUS versions 0.3 and prior
* GnuRADIUS versions 0.95 and prior
* ICRADIUS versions 0.18.1 and prior
* Livingston RADIUS versions 2.1 and earlier
* RADIUS (previously known as Lucent RADIUS) versions 2.1 and prior
* RADIUSClient versions 0.3.1 and prior
* XTRADIUS 1.1-pre1 and prior
* YARD RADIUS 1.0.19 and prior

I. Description

Two vulnerabilities in various implementations of RADIUS clients and
servers have been reported to several vendors and the CERT/CC. They
are remotely exploitable, and on most systems result in a denial of
service. VU#589523 may allow the execution of code if the attacker has
knowledge of the shared secret.

VU#589523 - Multiple implementations of the RADIUS protocol contain a
digest calculation buffer overflow

Multiple implementations of the RADIUS protocol contain a buffer
overflow in the function that calculates message digests.

During the message digest calculation, a string containing the
shared secret is concatenated with a packet received without
checking the size of the target buffer. This makes it possible to
overflow the buffer with shared secret data. This can lead to a
denial of service against the server. If the shared secret is known
by the attacker, then it may be possible to use this information to
execute arbitrary code with the privileges of the victim RADIUS
server or client, usually root. It should be noted that gaining
knowledge of the shared secret is not a trivial task.

Systems Affected by VU#589523

* Ascend RADIUS versions 1.16 and prior
* Cistron RADIUS versions 1.6.4 and prior
* FreeRADIUS versions 0.3 and prior
* GnuRADIUS versions 0.95 and prior
* ICRADIUS versions 0.18.1 and prior
* Livingston RADIUS versions 2.1 and earlier
* RADIUS (commonly known as Lucent RADIUS) versions 2.1 and prior
* RADIUSClient versions 0.3.1 and prior
* YARD RADIUS 1.0.19 and prior
* XTRADIUS 1.1-pre1 and prior

VU#936683 - Multiple implementations of the RADIUS protocol do not
adequately validate the vendor-length of vendor-specific attributes.

Various RADIUS servers and clients permit the passing of
vendor-specific and user-specific attributes. Several
implementations of RADIUS fail to check the vendor-length of
vendor-specific attributes. It is possible to cause a denial of
service against RADIUS servers with a malformed vendor-specific

RADIUS servers and clients fail to validate the vendor-length
inside vendor-specific attributes. The vendor-length shouldn't be
less than 2. If vendor-length is less than 2, the RADIUS server (or
client) calculates the attribute length as a negative number. The
attribute length is then used in various functions. In most RADIUS
servers the function that performs this calculation is rad_recv()
or radrecv(). Some applications may use the same logic to validate
user-specific attributes and be vulnerable via the same method.

Systems Affected by VU#936683

* Cistron RADIUS versions 1.6.5 and prior
* FreeRADIUS versions 0.3 and prior
* ICRADIUS versions 0.18.1 and prior
* Livingston RADIUS versions 2.1 and earlier
* YARD RADIUS 1.0.19 and prior
* XTRADIUS 1.1-pre1 and prior

II. Impact

Both of the vulnerabilities allow an attacker can cause a denial of
service of the RADIUS server. On some systems, VU#589523 may allow the
execution of code if the attacker has knowledge of the shared secret.

III. Solution

Apply a patch, or upgrade to the version specified by your vendor.
Block packets to the RADIUS server at the firewall

Limit access to the RADIUS server to those addresses which are
approved to authenticate to the RADIUS server. Note that this does not
protect your server from attacks originating from these addresses.

Appendix A. - Vendor Information

This appendix contains information provided by vendors for this
advisory. When vendors report new information to the CERT/CC, we
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their


Mac OS X and Mac OS X Server -- Not vulnerable since RADIUS is not
shipped with those products.


Cisco Systems has reviewed the following products that implement
RADIUS with regards to this vulnerability, and has determined that
the following are NOT vulnerable to this issue; Cisco IOS, Cisco
Catalyst OS, Cisco Secure PIX firewall, Cisco Secure Access Control
System for Windows, Cisco Aironet, Cisco Access Registrar, and
Cisco Resource Pooling Management Service. At this time, we are not
aware of any Cisco products that are vulnerable to the issues
discussed in this report.


You state 2 vulnerabilities:
1. Digest Calculation Buffer Overflow Vulnerability Cistron Radius up
to and including 1.6.4 is vulnerable
2. Invalid attribute length calculation on malformed Vendor-Specific
attr. Cistron Radius up to and including 1.6.5 is vulnerable

Today I have released version 1.6.6, which also fixes (2). The
homepage is on which you can also
find the ChangeLog. An announcement to the cistron-radius
mailinglist was also made today.

So everybody should upgrade to 1.6.6.


FreeBSD versions prior to 4.5-RELEASE (which is shipping today or
tomorrow or so) do contain some of the RADIUS packages mentioned
below: radiusd-cistron, freeradius, ascend-radius, icradius, and
radiusclient. However, 4.5-RELEASE will not ship with any of these
RADIUS packages, except radiusclient. Also, note that the
information you [CERT/CC] have forwarded previously indicates that
neither Merit RADIUS (radius-basic) nor radiusclient are


Fujitsu's UXP/V operating system is not vulnerable because UXP/V
does not support the Radius functionality.


The bug was fixed in version 0.96.


We have tested our Version of RADIUS, and we are NOT vulnerable.


IBM's AIX operating system, all versions, is not vulnerable as we
do not ship the RADIUS project with AIX.

Juniper Networks

Juniper products have been tested and are not affected by this

Lucent Technologies, Inc.

Lucent and Ascend "Free" RADIUS server Product Status

Reiteration of product End of Life
February 14, 2002

The purpose of this announcement is to make official the end of
life of products based on the Livingston Enterprises RADIUS server,
and to reiterate the terms of the original license.

Prior to the Lucent Technologies acquisition of Ascend Communications
and Livingston Enterprises, both companies distributed RADIUS servers
at no cost to their customers. The initial Livingston server was
RADIUS 1.16 followed in June 1999 by RADIUS 2.1. The Ascend server
was based on the Livingston 1.16 product with the most recent version
being released in June 1998. Lucent Technologies no longer
distributes these products, does not provide any support services for
these products, and has not done so for some time.

All of these products were distributed as-is without warranty,
under the BSD "Open Source" license with the following terms:

This software is provided by the copyright holders and contributors
``as is'' and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall the copyright
holder or contributors be liable for any direct, indirect,
incidental, special, exemplary, or consequential damages (including,
but not limited to, procurement of substitute goods or services;
loss of use, data, or profits; or business interruption) however
caused and on any theory of liability, whether in contract, strict
liability, or tort (including negligence or otherwise) arising in any
way out of the use of this software, even if advised of the
possibility of such damage.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the

* All advertising materials mentioning features or use of this
software must display the following acknowledgement:
This product includes software developed by Lucent Technologies and
its contributors.

* Neither the name of the copyright holder nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.

Under this license, other parties are free to develop and release
other products and versions. However, as noted in the license terns,
Lucent Technologies can not and does not assume any responsibility
for any releases, present or future, based on these products.

Replacement Product

The replacement product is NavisRadius 4.x. NavisRadius is a fully
supported commercial product currently available from Lucent
Technologies. Please visit the NavisRadius product web site at for product information and free
evaluation copies.

Richard Perlman
NavisRadius Product Management
Network Operations Software
[email protected]
+1 510-747-5650


We've completed our investigation into this issue based on the
information provided and have determined that no version of
Microsoft IAS is susceptible to either vulnerability.


Some of the affected radius daemons are available from NetBSD
pkgsrc. It is highly advisable that you update to the latest
versions available from pkgsrc. Also note that
pkgsrc/security/audit-packages can be used to notify you when new
pkgsrc related security issues are announced.

Process Software

MultiNet and TCPware do not provide a RADIUS implementation.

RADIUS (previously known as Lucent RADIUS)

I wish to advise that Lucent Radius 2.1 is vulnerable to VU#589523,
but is not vulnerable to VU#936683.

I have made an unofficial patch to this code to resolve this
problem. It will be released in
where previous patches to Radius by myself are available.


I've just uploaded version 0.3.2 of the radiusclient library to
which contains a fix for the reported buffer overflow.

Red Hat

We do not ship any radius software as part of any of our main
operating system. However, Cistron RADIUS was part of our
PowerTools add-on software CD from versions 5.2 through 7.1. Thus
while not installed by default, some users of Red Hat Linux may be
using Cistron RADIUSD. Errata packages that fix this problem and
our advisory will be available shortly on our web site at the URL
below. At the same time users of the Red Hat Network will be able
to update their systems to patched versions using the up2date tool.


The Caldera NON-Linux operating systems: OpenServer, UnixWare, and
Open UNIX, do not ship Radius servers or clients.


SGI does not ship with a RADIUS server or client, so we are not
vulnerable to these issues.

Wind River Systems

The current RADIUS client product from Wind River Systems, WindNet
RADIUS 1.1, is not susceptible to VU#936683 and VU#589523 in our
internal testing.

VU#936683 - WindNet RADIUS will pass the packet up to the
application. The application may need to be aware of the invalid
attribute length.

VU#589523 - WindNet RADIUS will drop the packet overflow.

Please contact Wind River support at [email protected] or call
(800) 458-7767 with any test reports related to VU#936683 and


We are trying to relase a new and fixed version of xtradius by the
end of the month (version 1.2.1).. Right now the new version is on
the CVS and we are testing it...


Current version 1.0.19 of Yardradius (which is derived from Lucent
2.1) seems suffering both the problems. I think I will release a
new version (1.0.20) which solves those buffer overflows before
your suggested date [3/4/2002].

Our thanks to 3APA3A and Joshua Hill and for
their cooperation, reporting and analysis of this vulnerability.

Feedback about this Advisory can be sent to the author,
Jason A. Rafail.

Appendix B. - References


This document is available from:

CERT/CC Contact Information

Email: [email protected]
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
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Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890

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Any material furnished by Carnegie Mellon University and the Software
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Copyright 2002 Carnegie Mellon University.

Revision History
March 04, 2002: Initial release

Version: PGP 6.5.8


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