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TUCoPS :: Web :: Apps :: ciaci024.txt

CGI Security Hold Ews1 1



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                   CGI Security Hole in EWS1.1 Vulnerability

January 21, 1998 18:00 GMT                                        Number I-024
PROBLEM:       A vulnerability exists in EWS1.1 (Excite for Web Servers,
               version 1.1).
PLATFORM:      Unix and Windows NT
DAMAGE:        If exploited, an unauthorized user may execute shell commands
               on the host system.
SOLUTION:      Apply the latest patches or workaround listed in Section III.
VULNERABILITY  Excite, Inc. urges you to act on this information as soon as
ASSESSMENT:    possible.

[ Start CERT Advisory ]

CERT* Vendor-Initiated Bulletin VB-98.01
Jan. 16, 1998
Issue Date: Jan. 19, 1998

Topic: CGI Security Hole in EWS1.1
Source: Excite, Inc.

To aid in the wide distribution of essential security information, the CERT
Coordination Center is forwarding the following information from Excite, Inc.
Excite, Inc. urges you to act on this information as soon as possible. Excite,
Inc. contact information is included in the forwarded text below; please
contact them if you have any questions or need further information.

=======================FORWARDED TEXT STARTS HERE============================

Topic: CGI Security Hole in EWS1.1

Source: Excite, Inc.

               555 Broadway, Redwood City, CA 94063

Problem: Vulnerability in EWS1.1, Unix and Windows NT platforms

I. Description

Excite for Web Servers, version 1.1, for Unix and Windows NT platforms,
contains a security hole that could allow a malicious user of the software
to execute shell commands on the the host system on which EWS has been
installed.  In situations where the web server is running under a user-id
with sufficient access privileges, a hacker could conceivably cause damage
to the host system.

EWS's search CGI is implemented in Perl and invokes a binary program to
actually perform the search against the corpus.  The function of the Perl
CGI is to parse the results from the search engine and render them in HTML.

This bug in no way affects, anyone visiting or searching, any search boxes (for example, those on the Netscape and
Microsoft sites) that point to, or sites that the Excite spider

II. Impact

Because a search entered by a user into the web page is passed as command
line argument to the search binary, and because the command line is
interpreted by the shell before the search binary is invoked, it is
possible for a hacker with sufficient know-how to craft a search that could
cause commands embedded in the search string to be invoked on the host

III. Solution

IMPORTANT: Please note that if you have obtained patches from Excite or a
third party site prior to 1/16/98, you do not have the most recent version
of the patch.  Please visit the patches page referenced below to obtain the
latest vresion of the patches, which have evaluated and tested internally,
as well as by CERT (

The security hole can be corrected by replacing single Perl library file
that is part of the EWS1.1 distribution.  There are two new versions of
this file available at  One
version is for Unix platforms, the other is for Windows NT platforms.
Changes are confined to two subroutines within the
library file.  The subroutines in question are 'MakeQuery' and

To apply the patch, simply replace the file, which
appears in the 'perllib' subdirectory of the EWS installation, with one of
the files posted at the URL provided above.  Note that comments at the top
of the file indicate which operating system it is intended for, either Unix
platforms, or Windows NT platforms.

For Unix platforms, the changes made to these routines invoke the search
binaries using Perl's 'exec', which calls C's execvp(3), thus bypassing any
shell processing of the command.  By avoiding shell processing of the
command, the security hole is closed and prevents any attacks using
shell-based hacking.

It is not possible to use the same solution in the Windows NT
implementation of Perl, so the patch for Windows NT takes a different
approach, by defining a set of legal characters for a search string, and
then 'sanitizing' the string by removing any characters that are not
members of the set of legal characters.

For more information, please visit

========================FORWARDED TEXT ENDS HERE=============================

[ End CERT Advisory ]


CIAC wishes to acknowledge the contributions of CERT for the
information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 510-422-8193
    FAX:      +1 510-423-8002
    STU-III:  +1 510-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
                        (or -- they're the same machine)
   Anonymous FTP:
                        (or -- they're the same machine)
   Modem access:        +1 (510) 423-4753 (28.8K baud)
                        +1 (510) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
3. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called Majordomo, which ignores E-mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-mail message body, substituting
ciac-bulletin, spi-announce OR spi-notes for list-name:

E-mail to or
        subscribe list-name
  e.g., subscribe ciac-bulletin

You will receive an acknowledgment email immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the email.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.

If you include the word 'help' in the body of an email to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via email, etc.

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California 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
disclosed, or represents that its use would not infringe 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 the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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