Snort Advisory: Integer Overflow in Stream4

[Brian Caswell <bmc () snort org>]

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Snort(TM) Advisory: Integer Overflow in Stream4 

Date: April 16, 2003


Affected Versions:
All versions of the following products are affected:

* Snort 1.8 through 1.9.1
* Snort CVS - current branch up to version 2.0.0 beta


Synopsis:
The Sourcefire Vulnerability Research Team has learned of an integer overflow 
in the Snort stream4 preprocessor used by the Sourcefire Network Sensor 
product line. The Snort stream4 preprocessor (spp_stream4) incorrectly 
calculates segment size parameters during stream reassembly for certain
sequence number ranges which can lead to an integer overflow that can be
expanded to a heap overflow.

The Snort stream4 flaw may lead to a denial of service (DoS) attack or 
remote command execution on a host running Snort. This attack can be launched 
by crafting TCP stream packets and transmitting them over a network segment 
that is being monitored by a vulnerable Snort implementation. In its 
default configuration, certain versions of snort are vulnerable to this 
attack, as is the default configuration of the Snort IDS.

Disabling the stream4 preprocessor will make the snort invulnerable to the 
attack.

To disable the stream4 preprocessor, edit snort.conf and replace any lines 
that begin with "preprocessor stream4" with "# preprocessor stream4"

NOTE: Disabling the stream4 preprocessor disables stateful inspection and 
stream reassembly and could allow someone to evade snort using tcp stream 
segmentation attacks.


Patches:

Snort 2.0 has been released and corrects this vulnerability.


(C) 2003 Sourcefire, Inc.  All rights reserved.
Sourcefire and Snort are trademarks or registered trademarks of Sourcefire, INC.
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