Re: WWW Security Hole
Thu, 12 Aug 93 15:36:19 EDT

I always suspected there might be a problem with the WWW paradigm
regarding security; specifically, what if one of the protocols is
general enough that commands specified in it could be legal for some
other protocol?

This concern is no longer academic. Check out the document

for a pointer to a document I consider somewhat dangerous. I only
know that this security hole will work in Xmosaic; haven't tested
other browsers but it seems reasonable to assume any browser with the
standard lib is vulnerable.

What does it do? It uses the gopher: scheme to cause your client to
attach to your local SMTP server and send a mail message to "root" on
your machine. The message is innocent but in principle it could be to
anyone and say anyone, and it would be tracable to you (depending what
kind of security logging your system does.)

A few questions:

- Is plain gopher sans WWW vulnerable to this same problem? Do they
know about it? If not, telling them (and also CERT) would be a good idea.

CERT knows about it:

CA-93:11 CERT Advisory
August 9, 1993
UMN UNIX gopher and gopher+ Vulnerabilities

The CERT Coordination Center has received information concerning
vulnerabilities in versions of the UMN UNIX gopher and gopher+ server and
client available before August 6, 1993. Vulnerable versions were available on,, and many other
anonymous FTP sites mirroring these software versions.

We strongly recommend that any site using versions of UMN UNIX gopher
and gopher+ dated prior to August 6, 1993 (including version 1.12, 1.12s,
2.0+, 2.03, and all earlier versions) immediately take corrective action.

If you have further questions regarding UMN UNIX gopher or gopher+ software,
send e-mail to:

I. Description

Several vulnerabilities have been identified in UMN UNIX gopher and
gopher+ when configured as a server or public access client.

Intruders are known to have exploited these vulnerabilities to obtain
password files. Other actions may also have been taken by intruders
exploiting these vulnerabilities. CERT has already contacted those
sites currently known to have been victims of these activities. However,
sites may want to check for weak passwords, or consider changing
passwords, after installing the new gopher software.

II. Impact

Anyone (remote or local) can potentially gain unrestricted access
to the account running the public access client, thereby permitting
them to read any files accessible to this account (possibly including
/etc/passwd or other sensitive files).

In certain configurations, anyone (remote or local) can potentially
gain access to any account, including root, on a host configured as a
server running gopherd.

III. Solution

Affected sites should consider disabling gopherd service and public gopher
logins until they have installed the new software.

New versions of the UMN UNIX gopher and gopher+ software have been
released that provide bug fixes and correct these security problems.
Sites can obtain these new versions via anonymous FTP from ( The files are located in:

Filename Size Checksum
-------- ------ -----------
/pub/gopher/Unix/gopher1.12S.tar.Z 306872 46311 300
/pub/gopher/Unix/gopher2.04.tar.Z 294872 29411 288

The CERT Coordination Center wishes to thank Matt Schroth, Williams College,
and others for informing us of these vulnerabilities. We would also like to
thank Paul Lindner, University of Minnesota, for his quick response to these

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

Internet E-mail:
Telephone: 412-268-7090 (24-hour hotline)
CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),
and are on call for emergencies during other hours.

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

Past advisories, information about FIRST representatives, and other information
related to computer security are available for anonymous FTP from

- How do we fix this? (Just throwing in a minor patch for this
particular attack is no good; we need a general solution for making
sure that a gopher: URL actually points to a gopher server.)

WWW should be a safe place, where I can just point a beginner and have
him wander around. This needs to be fixed, fast.

What I'm more concerned with now is your comments on the insecurity of WWW
itself. If this is clearly true, we will have to immediately pull it off all our machines
here (which we'll need to do if there isn't a "comfortable" answer to this...).
Once this is done, I suspect we'll never be able to put mosaic back.
I'm sure everyone across the board in corporate settings will have to do so also, so
let's see if we can resolve this QUICKLY and satisfactorily to keep WWW going strong.

(and hopefully my message will even get to the dist list...)

Rich Brandwein