-----BEGIN PGP SIGNED MESSAGE-----
AUSCERT External Security Bulletin Redistribution
ESB-97.088 -- CERT Vendor-Initiated Bulletin VB-97.06
Vulnerability in Lynx Downloading
16 July 1997
The CERT Coordination Center has released the following advisory concerning
a vulnerability in the Lynx program. This vulnerability may allow local
and remote users to execute arbitary commands with the privileges of the
user of Lynx.
The following security bulletin is provided as a service to AUSCERT's
members. As AUSCERT did not write this document, AUSCERT has had no
control over its content. As such, the decision to use any or all of this
information is the responsibility of each user or organisation, and should
be done so in accordance with site policies and procedures.
Contact information for this bulletin is included in the Security Bulletin
below. If you have any questions or need further information, please
contact them directly.
Previous advisories and external security bulletins can be retrieved from:
If you believe that your system has been compromised, contact AUSCERT or your
representative in FIRST (Forum of Incident Response and Security Teams).
Internet Email: email@example.com
Facsimile: (07) 3365 4477
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AUSCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for emergencies.
- --------------------------BEGIN INCLUDED TEXT--------------------
- -----BEGIN PGP SIGNED MESSAGE-----
CERT* Vendor-Initiated Bulletin VB-97.06
July 15, 1997
Topic: Vulnerability in Lynx Downloading
Source: Jim Spath
To aid in the wide distribution of essential security information, the CERT
Coordination Center is forwarding the following information from Jim Spath,
who coordinated this bulletin with several members of the lynx-dev mailing
list. They urge you to act on this information as soon as possible. Contact
information is included in the forwarded text below; please contact them if
you have any questions or need further information.
Questions about the bulletin only can be sent to Jim Spath
<firstname.lastname@example.org>; questions about Lynx can be sent to
=======================FORWARDED TEXT STARTS HERE============================
Lynx, on Un*x systems, may be coerced to read or execute arbitrary
files on the local system regardless of restrictions set by the
Installed versions of Lynx up to and including version 2.7.1 on Unix
or Unix-like operating systems are vulnerable.
A. Captive Lynx installations
Users of Lynx in a captive situation (where the Lynx user does not
normally have access to a shell prompt, or to a menu system that allows
the user to run arbitrary commands) can get access to a shell prompt.
This includes public Lynxes as well as any setup where the user
is restricted as to which programs can be run.
B. All Lynx installations
This vulnerability could also conceivably allow malicious webmasters to
add these carefully crafted URLs to their pages to cause unsuspecting
Lynx users (in captive accounts or otherwise) to execute arbitrary commands.
This vulnerability can be exploited by anyone who can provide Lynx a
carefully crafted URL.
If administrators of captive Lynxes cannot apply the code patches or
obtain updated binaries as described below, they are advised to disable
(g)oto on Lynx.
There is currently no workaround for impact "B" above. The code patches
below must be applied (or updated binaries obtained) to eliminate
Current developmental releases of Lynx have fixed this problem since
1997-06-26. Patches you may find from before that date may not
entirely eliminate the vulnerability.
The most recent stable version of Lynx (version 2.7.1) can be
patched to fix this problem by replacing the file "lynx2-7-1/src/LYDownload.c"
with a replacement file.
The replacement file to eliminate this vulnerability in version
2.7.1 is available (courtesy of Foteos Macrides) at:
All systems running Lynx versions 2.7.1 or earlier should be
updated to fix this problem.
Two development branches of the Lynx source code are available at:
Binary distributions of Lynx may be found at:
Note that producing binaries is a volunteer job and the latest (or any)
version may not be available for a specific platform.
V. Contact information
If you believe you have found a security problem with the current
version of Lynx, we urge you to forward it to the LYNX-DEV
mailing list at <email@example.com>.
The LYNX-DEV mailing list (with further information about this
vulnerability) is archived at:
Lynx security information is available at:
General information about Lynx is available at:
On-line help and documentation about Lynx is available using the
(h)elp command. More help is available in the source distribution.
Should your questions not be answered by these means, further
questions may be directed to <firstname.lastname@example.org>.
Please don't contact Lynx developers personally about Lynx-related
issues; please use either the mailing list or the "help" addresses
========================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 http://www.first.org/team-info/.
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
emergencies during other hours.
Fax +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
CERT publications, information about FIRST representatives, and other
security-related information are available from
CERT advisories and bulletins are also posted on the USENET newsgroup
To be added to our mailing list for CERT advisories and bulletins, send your
email address to
In the subject line, type
* Registered U.S. Patent and Trademark Office.
The CERT Coordination Center is part of the Software Engineering
Institute (SEI). The SEI is sponsored by the U. S. Department of Defense.
This file: ftp://info.cert.org/pub/cert_bulletins/VB-97.06.lynx
- -----BEGIN PGP SIGNATURE-----
- -----END PGP SIGNATURE-----
- --------------------------END INCLUDED TEXT--------------------
-----BEGIN PGP SIGNATURE-----
-----END PGP SIGNATURE-----