Re: [Snort-2003-001] Buffer overflow in Snort RPC p reprocessor

[Michael Anderson <mca () arlut utexas edu>]

I think this is an incorrect assumption.  Your snort's rpc preprocessor 
will read the traffic and be subject to malicious code regardless of 
whether your interface is stealth or not.  You could probably use the 
vulnerability to crash snort thus making you blind to other attacks.

-Mike

Slighter, Tim wrote:

> Should it - or could it be specified that users running snort on a stealth
> interface would not be impacted?
>
> -----Original Message-----
> From: Martin Roesch [mailto:roesch () sourcefire com]
> Sent: Monday, March 03, 2003 11:00 AM
> Subject: [Snort-users] [Snort-2003-001] Buffer overflow in Snort RPC
> preprocessor
>
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Snort Vulnerability Advisory [SNORT-2003-001]
>
> Date: 2003-03-03
>
> Affected Snort Versions:
>
> Any version starting with version 1.8 to those before 2003-03-03 1PM/ 
> US/Eastern including 1.9.0 and CVS HEAD (Snort 2.0beta)
>
> Synopsis:
>
> A buffer overflow has been found in the snort RPC normalization 
> routines by ISS X-Force.  This can cause snort to execute arbitrary 
> code embedded within sniffed network packets. This preprocessor is 
> enabled by default.
>
> Snort 1.9.1 has been released to resolve this issue. For users using 
> CVS HEAD, a fix has been committed to the source tree.
>
> Mitigation:
>
> If you are in an environment that can not upgrade snort immediately, 
> comment out the line in your snort.conf that begins:
>
> preprocessor rpc_decode
>
> and replace it with
>
> # preprocessor rpc_decode
>
> Details:
>
> When the rpc decoder normalizes fragmented RPC records, it incorrectly 
> checks the lengths of what is being normalized against the current 
> packet size.
>
> The rpc decoder in Snort 1.9.1 and above contains new alert options 
> that can be used to help detect this attack
>
> Option                    Default State
>
> alert_fragments           INACTIVE
> alert_large_fragments     ACTIVE
> alert_incomplete          ACTIVE
> alert_multiple_requests   ACTIVE
>
>
> The first option will alert on any rpc fragmented record it finds. 
> Large fragments will alert when the reassembled fragment record will 
> exceed the current packet length.  The incomplete record will alert 
> when there is a partial record found.  The alert_multiple_requests will 
> alert when we find more than one RPC request per packet ( or 
> reassembled packet ).
>
> Download Locations:
>
> Sourcefire has acquired additional bandwidth and hosting to aid users 
> wishing to upgrade their Snort implementation.  Binaries are currently 
> not available, this is a source release only at this time.  As new 
> binaries become available they will be added to the site.
>
> Source code: http://www.snort.org/dl/snort-1.9.1.tar.gz
> GPG Signatures: http://www.snort.org/dl/snort-1.9.1.tar.gz.asc
>
> CVS HEAD (Snort 2.0beta)  has been fixed as well.
>
> - -- 
> Martin Roesch - Founder/CTO, Sourcefire Inc. - (410)290-1616
> Sourcefire: Snort-based Enterprise Intrusion Detection Infrastructure
> roesch () sourcefire com - http://www.sourcefire.com
> Snort: Open Source Network IDS - http://www.snort.org
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>
>
>
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