Alt-N MDaemon's WorldClient Predictable Session ID Vulnerability

From: demetris papapetrou <>
Subject: Alt-N MDaemon's WorldClient Predictable Session ID Vulnerability

   Alt-N MDaemon's WorldClient Predictable Session ID Vulnerability

Software:  Alt-N MDaemon v13.0.3 and prior versions
Vuln Type: Session ID Prediction
Remote: Yes
Local: No
Discovered by: QSecure and Demetris Papapetrou
Discovered: 25/07/2012
Reported: 19/12/2012
Fixed: 15/01/2013 (
Disclosed: 18/02/2013

Alt-N WorldClient is the web interface of the MDaemon email server. It
has been identified that application session state is not maintained
by the user's session cookie but by the URL "Session" parameter
instead. This parameter is transmitted with every user request sent to
the WorldClient web application and under certain circumstances future
session IDs can be successfully predicted.

The use of predictable session IDs for authentication makes
WorldClient prone to session hijacking attacks. If the attacker can
generate a current valid session ID then he/she may be able to access
webmail accounts without possessing a valid username/password. The
impact of the attack is significantly reduced because WorldClient
associates the client's IP address with each session ID produced.
However, certain network setups or other scenarios may exist that
could render the IP restriction ineffective.

Alt-N MDaemon v13.0.3 & v12.5.6 were tested and found vulnerable;
other versions may also be affected.

1) The attacker needs to get a current or expired session ID.
       a) Google Search: "WorldClient.dll?Session="
       b) Steal an HTTP request and observe the Referer field
2) The MDaemon service or the machine has not been restarted since the
captured session ID was generated (There may be a way to deal with
this but further research is needed).

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