Great Circle Associates Firewalls
(October 1996)
 

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Subject: RE: Linux Network stack exploit
From: "Hicks, Rick" <RHicks @ hussmann . com>
Date: Fri, 25 Oct 1996 09:47:00 -0500
To: "'Firewalls List'" <firewalls @ greatcircle . com>

>Didn't know if all you "roll-your-own" types had seen this ...
>
>I don't currently run Linux, so I have not taken time to verify (or even   

>look closely)   - just passing it on.
>

I hope you're not attempting to take a shot at the "roll-your-own" folks   
(or Linux), as this problem affects more than just Linux.

I have personally verified that it crashes Linux, AIX, and HP-UX (which,   
for some reason, was left off the list of affected systems).  I can't   
verify Digital Unix, but I'll take their word for it.  Solaris and IRIX   
passed the test.

The bug can only be exploited from a system that runs the MS IP stack, as   
its ping command does no size checking.  Any other ping, as far as I   
know, will not allow you to specify the data size necessary to crash   
these systems.

I hesitated to post this (I've known since Sunday) because of the   
availability of patches for AIX and HP-UX.  Since it wasn't too secret   
then, and certainly less so now, I guess it doesn't matter.

>There is a nasty bug whereby AIX, Digital Unix, Linux and possibly some
>other systems can be brought down remotely by a suitably constructed
>oversize packet. Unfortunately a bug in another well known PC operating
>system means its easy to generate such packets.
>
>** This bug is being actively exploited on the internet against all the
>** mentioned systems. This fix should be considered essential as should
>** other equivalent vendor fixes
>
>The bug can be exploited as simply as;
>
>> 'ping -l 65510 host.running.linux'
>
>The following Linux fix drops such faulty frames and will also be   
included
>in 2.0.24
>
>Alan Cox
>
>[Patch also available from http://www.uk.linux.org/patches/]
>


________________________________________________
Rick Hicks
Systems Specialist
Hussmann Corporation
rhicks @
 hussmann .
 com
http://www.hussmann.com  


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