Broadcast crash in Popmessenger 1.60 (before 20 Sep 2004)

[Luigi Auriemma <aluigi@xxxxxxxxxxxxx>]

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                             Luigi Auriemma

Application:  PopMessenger
              http://www.leadmind.com
Versions:     <= 1.60 (before 20 Sep 2004)
Platforms:    Windows
Bug:          crash
Risk:         medium
Exploitation: remote (broadcast)
Date:         21 September 2004
Author:       Luigi Auriemma
              e-mail: aluigi@xxxxxxxxxxxxxx
              web:    http://aluigi.altervista.org


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1) Introduction
2) Bug
3) The Code
4) Fix


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===============
1) Introduction
===============


PopMessenger is a LAN messenger for Windows with some features.


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2) Bug
======


The messages exchanged with this program are encrypted with the
Blowfish algorithm and then converted to plain-text with Base64.

The problem is located just in the Base64 function because the program
shows an alert dialog if there are illegal chars in a message (like %
or _).
After about 15 consecutive dialogs the program definitely crashs.


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===========
3) The Code
===========


http://aluigi.altervista.org/poc/popmsgboom.zip


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4) Fix
======


The vendor has released a new version without changing the version
number (1.60).
All the programs downloaded after the 20 September 2004 are not
vulnerable.


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--- 
Luigi Auriemma
http://aluigi.altervista.org