OpenBSD 4.3/4.4/4.5 (IP datagrams) Remote DOS Vulnerability

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                           Helith - 0815
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Author		 : Rembrandt
Date		 : 2009-04-09
Affected Software: OpenBSD Kernel
Affected OS	 : OpenBSD 4.{3,4,5}, OpenBSD-current
		   Propably older versions are affected as well
Type		 : Denial of Service

OSVDB		 : 
Milw0rm		 : 
CVE		 : 
ISS X-Force:	 : 
BID		 : 
Secunia		 : 34676 
VUPEN ID	 : 

Trying to fix it responsible and get in contact with the vendor:

-- OpenBSD --
Contacted 		2009-04-09 15:35 GMT+1
Patch avaiable		2009-04-11 23:43 UTC

We received no response nor a notification about an upcoming patch by
the developers.
-- END --

OpenBSDs PF firewall in OpenBSD 4.3 up to OpenBSD-current is prone to a 
remote Denial of Service during a null pointer dereference in relation with
special crafted IP datagrams. If the firewall handles such a packet the kernel
panics.


Steps to reproduce:

If you are behind a OpenBSD firewall this nmap scan should trigger the problem
and crash your firewall device:

nmap -sO $some_host_so_that_the_firewall_handles_the_packets

For more informations please do read the patch issued by OpenBSD.


Patches and Workaround:

Patches are provided for OpenBSD 4.3, 4.4, 4.5 (upcoming, release 1st of may)
and OpenBSD-current (via CVS only) and are avaiable at the errata website.
The developers provide hints for a workaround at their errata website too.

Kind regards,
Rembrandt