(FreeBSD Issues Fix) w3m Text-based Web Browser May Execute Arbitrary Code
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SecurityTracker Alert ID: 1001969 |
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SecurityTracker URL: http://securitytracker.com/id/1001969
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CVE Reference:
GENERIC-MAP-NOMATCH
(Links to External Site)
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Date: Jul 11 2001
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Impact:
Execution of arbitrary code via network, User access via network
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): w3m 0.2.1
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Description:
Secure Net Service reported a vulnerability in the w3m text-based web browser that allows a remote web site to cause arbitrary code to be executed by the web browser.
The vulnerability is reportedly due to a buffer overflow in the processing of MIME headers. If a remote web site returns a malformed MIME header containing executable instructions to the w3m user, the malformed header could cause the code to be executed by the w3m browser with the privileges of the w3m user.
The vulnerability can reportedly be triggered by a MIME encoded header in base 64 format with more than 34 characters, such as the following header:
MIME header:
=?AAAAAAAAAAAAAA(50 'A' characters in the header)AAAAAAAA?=
A listing of the resulting memory dump and register contents is provided in the Source Message.
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Impact:
A remote web site could return a malformed MIME header containing code that will be executed by the w3m browser with the privileges of the w3m user.
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Solution:
The vendor has released a fix. See the Source Message for the vendor's advisory containing directions on how to obtain the appropriate fix.
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Vendor URL: ei5nazha.yz.yamagata-u.ac.jp/~aito/w3m/eng/index.html (Links to External Site)
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Cause:
Boundary error
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Underlying OS:
UNIX (FreeBSD)
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Message History:
This archive entry is a follow-up to the message listed below.
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Source Message Contents
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Date: Tue, 10 Jul 2001 07:38:10 -0700 (PDT)
Subject: FreeBSD Ports Security Advisory FreeBSD-SA-01:46.w3m
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-----BEGIN PGP SIGNED MESSAGE-----
=============================================================================
FreeBSD-SA-01:46 Security Advisory
FreeBSD, Inc.
Topic: w3m contains remotely exploitable buffer overflow
Category: ports
Module: w3m
Announced: 2001-07-10
Credits: OGASAWARA Satoshi (LAC / s.ogaswr@lac.co.jp)
KOBAYASHI Shigehiro (LAC / sigehiro@lac.co.jp)
Affects: Ports collection prior to the correction date.
Corrected: 2001-06-19
Vendor status: Updated version released
FreeBSD only: NO
I. Background
w3m is a console-based web browser.
II. Problem Description
The w3m port, versions prior to w3m-0.2.1_1, contains a buffer
overflow in the parsing of MIME headers. A malicious server which
is visited by a user with the w3m browser can exploit the browser
security holes in order to execute arbitrary code on the local
machine as the local user.
The w3m port is not installed by default, nor is it "part of
FreeBSD" as such: it is part of the FreeBSD ports collection, which
contains over 5400 third-party applications in a ready-to-install
format. The ports collection shipped with FreeBSD 4.3 is vulnerable
to this problem since it was discovered after its release.
FreeBSD makes no claim about the security of these third-party
applications, although an effort is underway to provide a security
audit of the most security-critical ports.
III. Impact
A malicious server which is visited by a user with the w3m browser
can exploit the browser security holes in order to execute arbitrary
code as the local user.
If you have not chosen to install the w3m port/package, then
your system is not vulnerable to this problem.
IV. Workaround
Deinstall the w3m port/package if you have installed it.
V. Solution
One of the following:
1) Upgrade your entire ports collection and rebuild the w3m port.
2) Deinstall the old package and install a new package dated after the
correction date, obtained from the following directories:
[i386]
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/www/w3m-ssl-0.2.1_1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/www/w3m-ssl-0.2.1_1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/www/w3m-ssl-0.2.1_1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/www/w3m-ssl-0.2.1_1.tgz
[alpha]
Packages are not automatically generated for the alpha architecture at
this time due to lack of build resources.
3) download a new port skeleton for the w3m port from:
http://www.freebsd.org/ports/
and use it to rebuild the port.
4) Use the portcheckout utility to automate option (3) above. The
portcheckout port is available in /usr/ports/devel/portcheckout or the
package can be obtained from:
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz
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