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CA-2003-10 Integer overflow in Sun RPC XDR library routines


CERT Advisory CA-2003-10 Integer overflow in Sun RPC XDR library routines

Original release date: March 19, 2003
Last revised: --
Source: CERT/CC

A complete revision history can be found at the end of this file.

Systems Affected

Applications using vulnerable implementations of SunRPC-derived XDR
libraries, which include
* Sun Microsystems network services library (libnsl)
* BSD-derived libraries with XDR/RPC routines (libc)
* GNU C library with sunrpc (glibc)


There is an integer overflow in the xdrmem_getbytes() function
distributed as part of the Sun Microsystems XDR library. This overflow
can cause 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

I. Description

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
xdrmem_getbytes() function in the XDR library provided by Sun
Microsystems contains an integer overflow that can lead to improperly
sized dynamic memory allocation. Depending on how and where the
vulnerable xdrmem_getbytes() function is used, subsequent problems
like buffer overflows may result.

Researchers at eEye Digital Security discovered this vulnerability and
have also published an advisory. This issue is currently being tracked
as VU#516825 by the CERT/CC and as CAN-2003-0028 in the Common
Vulnerabilities and Exposures (CVE) dictionary. Note that this
vulnerability is similar to, but distinct from, VU#192995.

II. Impact

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
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 crash the rpcbind
service and possibly execute arbitrary code with root privileges. In
addition, intruders may be able to crash the MIT KRB5 kadmind or cause
it to leak sensitive information, such as secret keys.

III. Solution

Apply a patch from your vendor

Apply the appropriate patch or upgrade as specified by your vendor.
See Appendix A below and the Systems Affected section of VU#516825 for
further information.

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:
1. Patch or obtain updated XDR/RPC libraries.
2. Restart any dynamically linked services that make use of the
XDR/RPC libraries.
3. Recompile any statically linked applications using the patched or
updated XDR/RPC libraries.

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 xdrmem_getbytes() function.

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, we have not received their

Apple Computer, Inc.

Mac OS X and Mac OS X Server do not contain the vulnerabilities
described in this report.

Cray, Inc.

Cray Inc. may be vulnerable and has opened spr's 724153 and 724154 to


We are currently investigating how the vulnerability reported under
VU#516825 affects the Fujitsu UXP/V O.S. We will update this statement
as soon as new information becomes available.

GNU glibc

Version 2.3.1 of the GNU C Library is vulnerable. Earlier versions are
also vulnerable. The following patches have been installed into the
CVS sources, and should appear in the next version of the GNU C
Library. These patches are also available from the following URLs:

2002-12-16 Roland McGrath

* sunrpc/xdr_mem.c (xdrmem_inline): Fix argument type.
* sunrpc/xdr_rec.c (xdrrec_inline): Likewise.
* sunrpc/xdr_stdio.c (xdrstdio_inline): Likewise.

2002-12-13 Paul Eggert

* sunrpc/rpc/xdr.h (struct XDR.xdr_ops.x_inline): 2nd arg
is now u_int, not int.
(struct XDR.x_handy): Now u_int, not int.
* sunrpc/xdr_mem.c: Include .
(xdrmem_getlong, xdrmem_putlong, xdrmem_getbytes, xdrmem_putbytes,
xdrmem_inline, xdrmem_getint32, xdrmem_putint32):
x_handy is now unsigned, not signed.
Do not decrement x_handy if no change is made.
(xdrmem_setpos): Check for int overflow.
* sunrpc/xdr_sizeof.c (x_inline): 2nd arg is now unsigned.
(xdr_sizeof): Remove cast that is now unnecessary, now that
x_handy is unsigned.

[ text of diffs available in the links included above --CERT/CC ]

Hewlett-Packard Company

RE: HP Case ID SSRT2439

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.


Hitachi's GR2000 gibabit router series - is NOT vulnerable.

IBM Corporation

The AIX operating system is vulnerable to the issues discussed in CERT
vulnerability note VU#516825 in releases 4.3.3, 5.1.0 and 5.2.0.

IBM provides the following official fixes:

APAR number for AIX 4.3.3: IY38524
APAR number for AIX 5.1.0: IY38434
APAR number for AIX 5.2.0: IY39231

Please contact your local IBM AIX support center for any assistance.

Ingrian Networks

Ingrian Networks products are not succeptable to the vulnerabilities
in VU#516825.

MIT Kerberos Development Team

It may be possible for a remote attacker to exploit an integer
overflow in xdrmem_getbytes() to crash the kadmind server process by a
read segmentation fault. For this to succeed, the kadmind process must
be able to allocate more than MAX_INT bytes of memory. This is
believed to be unlikely, as most installations are not likely to
permit that the allocation of that much memory.

It may also be possible for a remote attacker to exploit this integer
overflow to obtain sensitive information, such as secret keys, from
the kadmind process. This is believed to be extremely unlikely, as
there are unlikely to be ways for the information, once improperly
copied, of being returned to the attacker. In addition, the above
condition of the kadmind being able to allocate huge amounts of memory
must be satisfied.
Please see

This patch may also be found at:

The associated detached PGP signature is at:

NEC Corporation

[Server Products] * EWS/UP 48 Series operating system - is NOT


The length types of the various xdr*_getbytes functions were made
consistent somewhere back in 1997 (all u_int), so we're not vulnerable
in that area.

Network Appliance

NetApp products are not vulnerable to this issue.


This issue has no relationship to the product we ship.


SGI acknowledges receiving CERT VU#516825 and is currently
investigating. This is being tracked as SGI Bug# 880925. No further
information is available at this time.

For the protection of all our customers, SGI does not disclose,
discuss or confirm vulnerabilities until a full investigation has
occurred and any necessary patch(es) or release streams are available
for all vulnerable and supported SGI operating systems. Until SGI has
more definitive information to provide, customers are encouraged to
assume all security vulnerabilities as exploitable and take
appropriate steps according to local site security policies and
requirements. As further information becomes available, additional
advisories will be issued via the normal SGI security information
distribution methods including the wiretap mailing list on

Sun Microsystems

Solaris 2.6, 7, 8 and 9 are vulnerable to VU#516825.
Sun will be publishing a Sun Alert for the issue at the following
location shortly:
The Sun Alert will be updated with the patch information as soon as
the patches are available.
At that time, the patches listed in the Sun Alert will be available

Appendix B. - References

1. AD20030318.html -
2. VU#192995 -
3. VU#516825 -
4. RFC1831 -
5. RFC1832 -

Thanks to Riley Hassell of eEye Digital Security for discovering and
reporting this vulnerability. Thanks also to Sun Microsystems for
additional technical details.

Authors: Chad Dougherty and Jeffrey Havrilla

This document is available from:

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Revision History
Mar 19, 2003: Initial release

Version: PGP 6.5.8


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