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CA-2002-10 Format String Vulnerability in rpc.rwalld


CERT Advisory CA-2002-10 Format String Vulnerability in rpc.rwalld

Original release date: May 1, 2002
Last revised: --
Source: CERT/CC

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

Systems Affected

* Sun Solaris 2.5.1, 2.6, 7, and 8


The rwall daemon (rpc.rwalld) is a utility that is used to listen for
wall requests on the network. When a request is received, it calls
wall, which sends the message to all terminals of a time-sharing
system. A format string vulnerability may permit an intruder to
execute code with the privileges of the rwall daemon. A proof of
concept exploit is publicly available, but we have not seen active
scanning or exploitation of this vulnerability.

I. Description

rpc.rwalld is a utility that listens for remote wall requests. Wall is
used to send a message to all terminals of a time-sharing system. If
the wall command cannot be executed, the rwall daemon will display an
error message.

An intruder can consume system resources and potentially prevent wall
from executing, which would trigger the rwall daemon's error message.
A format string vulnerability exists in the code that displays the
error message. This vulnerability may permit the intruder to execute
code with the privileges of the rwall daemon.

This vulnerability may be exploited both locally and remotely,
although remote exploitation is significantly more difficult.

II. Impact

An intruder can execute code with the privileges of the rwall daemon,
typically root.

III. Solution

Apply a patch

Appendix A contains information provided by vendors for this advisory.

If a patch is not available, disable the rwall daemon (rpc.rwalld) in
inetd.conf until a patch can be applied.

If disabling the rwall daemon is not an option, implement a firewall
to limit access to rpc.rwalld (typically port 32777/UDP). Note that
this will not mitigate all vectors of attack.

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, please check the Vulnerability
Note (VU#638099) or contact your vendor directly.


HP is not vulnerable.


IBM's AIX operating system, versions 4.3.x and 5.1L, is not
susceptible to the vulnerability described.


NetBSD has never been vulnerable to this problem.

Sun Microsystems

Sun confirms that there is a format string vulnerability in
rpc.rwalld(1M) which affects Solaris 2.5.1, 2.6, 7 and 8. However,
this issue relies on a combination of events, including the
exhaustion of system resources, which are difficult to control by a
remote user in order to be exploited. Disabling rpc.rwalld(1M) in
inetd.conf(4) is the recommended workaround until patches are

Sun is currently generating patches for this issue and will be
releasing a Sun Security Bulletin once the patches are available.
The bulletin will be available from:

Sun patches are available from:

The CERT Coordination Center acknowledges "GOBBLES" as the discoverer
of this vulnerability and thanks Sun Microsystems for their technical

Feedback can be directed to the author: Jason A. Rafail

This document is available from:

CERT/CC Contact Information

Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890

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Copyright 2002 Carnegie Mellon University.

Revision History
May 1, 2002: Initial release

Version: PGP 6.5.8


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