Archive of CERT general posting, CERT Vendor-Initiated Bulletin VB-98.01 - excite

20/01/98, CERT Vendor-Initiated Bulletin VB-98.01 - excite
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Subject: CERT Vendor-Initiated Bulletin VB-98.01 - excite
From: CERT Bulletin <>
Date: Mon, 19 Jan 1998 09:56:39 -0500
Organization: CERT(sm) Coordination Center - +1 412-268-7090


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=============================

If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident Response
and Security Teams (FIRST). See

We strongly urge you to encrypt any sensitive information you send by email.
The CERT Coordination Center can support a shared DES key and PGP. Contact
the CERT staff for more information.

Location of CERT PGP key

CERT Contact Information
- ------------------------

Phone    +1 412-268-7090 (24-hour hotline)
                CERT personnel answer 8:30-5:00 p.m. EST
                (GMT-5)/EDT(GMT-4), and are on call for
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Fax      +1 412-268-6989

Postal address
        CERT Coordination Center
        Software Engineering Institute
        Carnegie Mellon University
        Pittsburgh PA 15213-3890

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The CERT Coordination Center is part of the Software Engineering
Institute (SEI). The SEI is sponsored by the U. S. Department of Defense.

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