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EMERGENCY RESPONSE SERVICE
SECURITY VULNERABILITY ALERT
11 February 1998 13:30 GMT Number: ERS-SVA-E01-1998:003.1
===============================================================================
VULNERABILITY SUMMARY
VULNERABILITY: Telnet denial of service attack
PLATFORMS: IBM AIX(r) 4.1.x, 4.2.x, 4.3
SOLUTION: Apply the fixes listed below.
THREAT: Remote users can cause the system to hang.
===============================================================================
DETAILED INFORMATION
I. Description
A denial of service attack has been posted to the Bugtraq mailing list
that causes all tty activity to hang and prevents new telnet sessions
from being established.
II. Impact
Remote users can cause the system to run out of message blocks and
hang.
III. Solutions
A. Official fix
At this time, only the AIX 4.1.x APAR is available. AIX 4.2.x
and 4.3.0 customers can apply the temporary fix listed below
until the official APARs are available. There are no fixes
planned for AIX 3.2.5 or earlier. It is recommended that version
3 customers upgrade to version 4.
AIX 4.1.x: IX73427 (bos.rte.tty 4.1.5.20) -- available now
AIX 4.2.x: IX73580
AIX 4.3.0: IX73214
B. How to alleviate the problem
A temporary fix is available for AIX 4.2.x and AIX 4.3.0 via
anonymous ftp from:
ftp://aix.software.ibm.com/aix/efixes/security/ldterm_fix.tar.Z
Filename sum md5
===================================================================
ldterm.42 52419 77 7ec3ff7eb83ded8f50219a838a0a4c0b
ldterm.43 37579 77 f066b7d6c3a845c892941a7ab15a6e60
ldterm_fix.sh 10210 3 e3a8bbecda52ff68391657f008b46262
Use the following steps (as root) to install the temporary fix:
1. Use the following command to determine the version of the
bos.rte.tty fileset on your machine.
# lslpp -l bos.rte.tty
If the version is not at the level described below, install
the requisite APAR for your release. This will help ensure
that the efix binary will run properly.
Release bos.rte.tty version requisite APAR
=============================================================
AIX 4.2.x less than 4.2.1.9 install IX73755
AIX 4.3.0 less than 4.3.0.3 install IX73397
2. Uncompress and extract the fix.
# uncompress < ldterm_fix.tar.Z | tar xf -
# cd ldterm_fix
3. Run the ldterm_fix.sh script to install the new tty driver.
# ./ldterm_fix.sh
4. Reboot.
NOTE: This temporary fix has not been fully regression tested.
IV. Obtaining Fixes
IBM AIX APARs may be ordered using Electronic Fix Distribution (via the
FixDist program), or from the IBM Support Center. For more information
on FixDist, and to obtain fixes via the Internet, please reference
http://service.software.ibm.com/aixsupport/
or send electronic mail to "aixserv@austin.ibm.com" with the word
"FixDist" in the "Subject:" line.
V. Acknowledgements
Thanks to Kevin Ruderman <rudi@bu.edu> for bringing this problem to our
attention.
VI. Contact Information
Comments regarding the content of this announcement can be directed to
the IBM Support Center or to:
security-alert@austin.ibm.com
To request the PGP public key that can be used to encrypt new AIX
security vulnerabilities, send email to security-alert@austin.ibm.com
with a subject of "get key".
If you would like to subscribe to the AIX security newsletter, send a
note to aixserv@austin.ibm.com with a subject of "subscribe Security".
To cancel your subscription, use a subject of "unsubscribe Security".
To see a list of other available subscriptions, use a subject of
"help".
IBM and AIX are a registered trademark of International Business
Machines Corporation. All other trademarks are property of their
respective holders.
===============================================================================
IBM's Internet Emergency Response Service (IBM-ERS) is a subscription-based
Internet security response service that includes computer security incident
response and management, regular electronic verification of your Internet
gateway(s), and security vulnerability alerts similar to this one that are
tailored to your specific computing environment. By acting as an extension
of your own internal security staff, IBM-ERS's team of Internet security
experts helps you quickly detect and respond to attacks and exposures across
your Internet connection(s).
As a part of IBM's Business Recovery Services organization, the IBM Internet
Emergency Response Service is a component of IBM's SecureWay(tm) line of
security products and services. From hardware to software to consulting,
SecureWay solutions can give you the assurance and expertise you need to
protect your valuable business resources. To find out more about the IBM
Internet Emergency Response Service, send an electronic mail message to
ers-sales@vnet.ibm.com, or call 1-800-742-2493 (Prompt 4).
IBM-ERS maintains a site on the World Wide Web at http://www.ers.ibm.com/.
Visit the site for information about the service, copies of security alerts,
team contact information, and other items.
IBM-ERS uses Pretty Good Privacy* (PGP*) as the digital signature mechanism for
security vulnerability alerts and other distributed information. The IBM-ERS
PGP* public key is available from http://www.ers.ibm.com/team-info/pgpkey.html.
"Pretty Good Privacy" and "PGP" are trademarks of Philip Zimmermann.
IBM-ERS is a Member Team of the Forum of Incident Response and Security Teams
(FIRST), a global organization established to foster cooperation and response
coordination among computer security teams worldwide.
Copyright 1998 International Business Machines Corporation.
The information in this document is provided as a service to customers of
the IBM Emergency Response Service. Neither International Business Machines
Corporation, Integrated Systems Solutions Corporation, nor any of their
employees, makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness, or usefulness of
any information, apparatus, product, or process contained herein, or
represents that its use would not infringe any privately owned rights.
Reference herein to any specific commercial products, process, or service by
trade name, trademark, manufacturer, or otherwise, does not necessarily
constitute or imply its endorsement, recommendation or favoring by IBM or
its subsidiaries. The views and opinions of authors expressed herein do not
necessarily state or reflect those of IBM or its subsidiaries, and may not be
used for advertising or product endorsement purposes.
The material in this security alert may be reproduced and distributed,
without permission, in whole or in part, by other security incident response
teams (both commercial and non-commercial), provided the above copyright is
kept intact and due credit is given to IBM-ERS.
This security alert may be reproduced and distributed, without permission,
in its entirety only, by any person provided such reproduction and/or
distribution is performed for non-commercial purposes and with the intent of
increasing the awareness of the Internet community.
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