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PHP-Nuke mail CRLF Injection vulnerabilities
From: Ulf Harnhammar <ulfh () update uu se>
Date: Fri, 20 Dec 2002 11:32:21 +0100 (CET)

PHP-Nuke mail CRLF Injection vulnerabilities

VENDOR: Fransisco Burzi et al.
HOMEPAGE: http://phpnuke.org/
VULNERABLE VERSIONS: 6.0 (the only supported version)
IMMUNE VERSIONS: 6.0 with my patch applied


"PHP-Nuke is a Web portal and online community system which
includes Web-based administration, surveys, access statistics,
user customizable boxes, a themes manager for registered users,
friendly administration GUI with graphic topic manager, the
ability to edit or delete stories, an option to delete comments,
a moderation system, referer tracking, integrated banner ad system,
search engine, backend/headlines generation (RSS/RDF format), Web
directory like Yahoo, events manager, and support for 20+ languages."

(direct quote from the program's project page at Freshmeat)

PHP-Nuke is published under the terms of the GNU General Public
License. It is a very popular program with lots and lots of
installations. It is included as one of the packages in Debian
GNU/Linux and one of FreeBSD's ports.

Despite all this, the program has a bad reputation regarding
security matters.


PHP-Nuke has got four functions that allow restricted sending of
e-mails: Feedback, Recommend Us, Send (news item) to a Friend and
Send this Journal to a Friend. They either restrict who you can send
e-mails to or what message you can send to them. They are open for
anonymous users as well as regular users.

By submitting special data, an attacker can escape these restrictions
and use someone else's PHP-Nuke installation to send HTML e-mails
to any recipient with any message that they like.


The fourth parameter to PHP's mail() function contains the additional
mail headers that PHP doesn't have a special parameter for. In this
case, it's used to add From and Reply-To headers. When PHP-Nuke
constructs the value for this parameter, it doesn't check the form
data it's using for CR and LF characters. As a result, an attacker
can supply extra mail headers and even an extra mail body, and they
will be included in the mail between the real headers and the real
body. This is done by simply including CR and LF characters in the
form data field that contains your e-mail address. If the attacker
includes an HTML message ending with a "<!--" tag or a
"<font color='something'>" tag that sets the foreground colour to
the background colour, the real mail body will not be shown in
many programs.


I didn't contact the vendor, as Fransisco has a very bad track
record when it comes to replying to security reports.


Instead I wrote an unofficial patch for this issue. I have patched
against version 6.0.

The patch simply replaces all CR and LF characters in the vulnerable
variables with spaces, and then the exploit doesn't work anymore.

// Ulf Harnhammar
   VSU Security
   ulfh () update uu se

"I saw the worst minds of my generation / getting their political
 information from tabloids / listening to Savage Garden's greatest
 hits / getting married and having kids at 25 just 'cause the
 neighbours did / and building the worst administrative web-based
 members interface ever known to man" (To B.)

Attachment: php-nuke_mail_crlf.patch

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