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bogofilter-SA-2010-01

Topic:		heap corruption overrun in bogofilter/bogolexer

Announcement:	bogofilter-SA-2010-01
Writer:		Matthias Andree
Version:	1.0
CVE ID:		CVE-2010-2494
Announced:	2010-07-07
Category:	vulnerability
Type:		array index underflow/out of bounds write through invalid input
Impact:		heap corruption, application crash
Credits:	Julius Plenz
Danger:		medium
URL:		http://bogofilter.sourceforge.net/security/bogofilter-SA-2010-01

Affected:	bogofilter <= 1.2.1
		SVN checkouts before 2010-07-03 08:40 UTC

Not affected:	bogofilter 1.2.2

1. Background
=============

Bogofilter is a software package for classifying a message as spam or
non-spam.  It uses a data base to store words and must be trained
which messages are spam and non-spam. It uses the probabilities of
individual words for classifying the message.

Note that the bogofilter project is issuing security announcements only
for current "stable" releases, and not necessarily for past "stable"
releases.

2. Problem description
======================

Bogofilter's/bogolexer's base64 could overwrite memory before its heap
buffer if the base64 input started with an equals sign, such as through
misdeclaration of quoted-printable as base64.

3. Impact
=========

Vulnerable bogofilter and bogolexer applications can corrupt their heap and
crash. The consequences are dependent on the local configuration, memory
layout and operating system features.

4. Solution
===========

Upgrade your bogofilter to version 1.2.2 (or a newer release).
This version may not yet be available when this security announcement is
issued.

bogofilter is available from SourceForge:
<https://sourceforge.net/project/showfiles.php?group_id=62265>


Alternatively, this patch to 1.2.1 would fix the issue:
(Note that if you see "- -" at the beginnings of these lines,
you need to run this file through gnupg or pgp to strip the signature
and the "-"-escaping, or manually replace such line beginnings with
"-"). This is an SVN diff of base64.c between revisions 6766 and 6906
and comprises two change sets: 6904 and 6906.

- --- ./src/base64.c	2009/01/12 04:27:36	6766
+++ ./src/base64.c	2010/07/03 08:39:44	6906
@@ -61,8 +61,10 @@
 	    d[i] = c;
 	    v = v >> 8;
 	}
- -	d += 3 - shorten;
- -	count += 3 - shorten;
+    if(shorten != 4) {
+        d += 3 - shorten;
+        count += 3 - shorten;
+    }
     }
     /* XXX do we need this NUL byte? */
     if (word->leng)


A. Copyright, License and Warranty
==================================

(C) Copyright 2010 by Matthias Andree, <matthias.andree@gmx.de>.
Some rights reserved.

This work is dual-licensed under the
Creative Commons Attribution-NoDerivs 3.0 Germany License (CC BY-ND 3.0),
and the GNU General Public License, v3, or later.

To view a copy of the Creative Commons Attribution-NoDerivs 3.0
Germany license, visit
http://creativecommons.org/licenses/by-nd/3.0/de/deed.en or send a
letter to:

Creative Commons
444 Castro Street
Suite 900
MOUNTAIN VIEW, CALIFORNIA 94041
USA


This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program, in the file ../gpl-3.0.txt.
If not, see <http://www.gnu.org/licenses/>.


THIS WORK IS PROVIDED FREE OF CHARGE AND WITHOUT ANY WARRANTIES.
Use the information herein at your own risk.


END of bogofilter-SA-2010-01
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