CERT® Advisory CA-2002-25 Integer Overflow In XDR LibraryOriginal release date: August 05, 2002
Last revised: October 03, 2002
A complete revision history can be found at the end of this file.
Systems AffectedApplications using vulnerable implementations of SunRPC-derived XDR libraries, which include, but are not limited to:
There is an integer overflow present in the xdr_array() function distributed as part of the Sun Microsystems XDR library. This overflow has been shown to lead to remotely exploitable buffer overflows in multiple applications, leading to the execution of arbitrary code. Although the library was originally distributed by Sun Microsystems, multiple vendors have included the vulnerable code in their own implementations.
The XDR (external data representation) libraries are used to provide platform-independent methods for sending data from one system process to another, typically over a network connection. Such routines are commonly used in remote procedure call (RPC) implementations to provide transparency to application programmers who need to use common interfaces to interact with many different types of systems. The xdr_array() function in the XDR library provided by Sun Microsystems contains an integer overflow that can lead to improperly sized dynamic memory allocation. Subsequent problems like buffer overflows may result, depending on how and where the vulnerable xdr_array() function is used.
Because SunRPC-derived XDR libraries are used by a variety of vendors in a variety of applications, this defect may lead to a number of differing security problems. Exploiting this vulnerability will lead to denial of service, execution of arbitrary code, or the disclosure of sensitive information.
Specific impacts reported include the ability to execute arbitrary code with root privileges (by exploiting dmispd, rpc.cmsd, or kadmind, for example). In addition, intruders who exploit the XDR overflow in MIT KRB5 kadmind may be able to gain control of a Key Distribution Center (KDC) and improperly authenticate to other services within a trusted Kerberos realm.
Apply a patch from your vendor
Appendix A contains information provided by vendors for this advisory. As vendors report new information to the CERT/CC, we will update this section and note the changes in our revision history. If a particular vendor is not listed below or in the vulnerability note, we have not received their comments. Please contact your vendor directly.
Note that XDR libraries can be used by multiple applications on most systems. It may be necessary to upgrade or apply multiple patches and then recompile statically linked applications.
Applications that are statically linked must be recompiled using patched libraries. Applications that are dynamically linked do not need to be recompiled; however, running services need to be restarted in order to use the patched libraries.
System administrators should consider the following process when
addressing this issue:
Disable access to vulnerable services or applications
Until patches are available and can be applied, you may wish to
disable access to services or applications compiled with the
vulnerable xdr_array() function. Such applications include, but
are not limited to, the following:
As a best practice, the CERT/CC recommends disabling all services that are not explicitly required.
Appendix A. - Vendor Information
This appendix contains information provided by vendors for this advisory. As vendors report new information to the CERT/CC, we will update this section and note the changes in our revision history. If a particular vendor is not listed below or in the individual vulnerability notes, we have not received their comments.
Apple Computer, Inc.
The vulnerability described in this note is fixed with Security Update 2002-08-02.
The Debian GNU/Linux distribution was vulnerable with regard to the
the XDR problem as stated above with the following vulnerability
However, the following advisories were raised recently which contain
and announced fixes:
DSA 142-1 OpenAFS (safe version are: 1.2.3final2-6 (woody) and 1.2.6-1 (sid))
The advisory for the GNU libc is pending, it is currently being
recompiled. The fixed versions will probably be:
Debian 2.2 (potato) glibc 2.1.3-23 or later
Version 2.2.5 and earlier versions of the GNU C Library are
vulnerable. For Version 2.2.5, we suggest the following patch. This
patch is also available from the GNU C Library CVS repository at:
2002-08-02 Jakub Jelinek <email@example.com>
SOURCE: Hewlett-Packard Company
RE: Potential RPC XDR buffer overflow
At the time of writing this document, Hewlett Packard is currently investigating the potential impact to HP's released operating System software products.
As further information becomes available HP will provide notice of the availability of any necessary patches through standard security bulletin announcements and be available from your normal HP Services support channel.
IBM is vulnerable to the above XDR Library issues in both the 4.3
and 5.1 releases of AIX. A temporary patch is currently available
through an efix pacakge. Efixes are available from
The following APARs will be available in the near future:
AIX 4.3.3: APAR #IY34194 ( available approx 10/1/2002 )
The Juniper Networks SDX-300 Service Deployment System (SSC) does use XDR for communication with an ERX edge router, but does not make use of the Sun RPC libraries. The SDX-300 product is not vulnerable to the Sun RPC XDR buffer overflow as outlined in this CERT advisory.
KTH and Heimdal Kerberos
kth-krb and heimdal are not vulnerable to this problem since they do not use any Sun RPC at all.
MIT Kerberos Development Team
The patch is available directly:
The following detached PGP signature should be used to verify the authenticity and integrity of the patch:
Microsoft is currently conducting an investigation based on this report. We will update this advisory with information once it is complete.
NetApp systems are not vulnerable to this problem.
OpenAFS is an affected vendor for this vulnerability. http://www.openafs.org/pages/security/OPENAFS-SA-2002-001.txt details how we have dealt with the issue.
The xdr_array(3) integer overflow was present in the glibc package on
Openwall GNU/*/Linux until 2002/08/01 when it was corrected for
Owl-current and documented as a security fix in the system-wide change
log available at:
The same glibc package update also fixes a very similar but different calloc(3) integer overflow possibility that is currently not known to allow for an attack on a particular application, but has been patched as a proactive measure. The Sun RPC xdr_array(3) overflow may allow for passive attacks on mount(8) by malicious or spoofed NFSv3 servers as well as for both passive and active attacks on RPC clients or services that one might install on Owl. (There're no RPC services included with Owl.)
Red Hat distributes affected packages glibc and Kerberos in all Red Hat Linux distributions. We are currently working on producing errata packages, when complete these will be available along with our advisory at the URLs below. At the same time users of the Red Hat Network will be able to update their systems using the 'up2date' tool.
SGI now has patches available to fix this problem, per 20020801-01-P:
Sun Microsystems, Inc.
Sun can confirm that there is a type overflow vulnerability in the
xdr_array(3NSL) function which is part of the network services library,
libnsl(3LIB), on Solaris 2.5.1 through 9. Sun has published Sun Alert
46122 which describes the issue, applications affected, and workaround
information. The Sun Alert will be updated as more information or patches
become available and is located here:
Sun will be publishing a Sun Security Bulletin for this issue once all of
the patches are available which will be located at:
Appendix B. - References
Thanks to Sun Microsystems for working with the CERT/CC to make this document possible. The initial vulnerability research and demonstration was performed by Internet Security Systems (ISS).
This document is available from: http://www.cert.org/advisories/CA-2002-25.html
CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends.
We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from
If you prefer to use DES, please call the CERT hotline for more information.
Getting security information
CERT publications and other security information are available from our web site
* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.
Conditions for use, disclaimers, and sponsorship information
Copyright 2002 Carnegie Mellon University.
Aug 05, 2002: Initial release Aug 06, 2002: Minor update to Debian statement, corrected glibc for Debian 3.0 (woody) will be 2.2.5-11.1 or later Aug 06, 2002: Added IBM statement Aug 19, 2002: Updated SGI statement Sep 03, 2002: Updated IBM statement Oct 03, 2002: Added Microsoft Bulletin MS02-057 to list of references