_   _ _____ _     ___ _____ _   _
                   / / / / ____/ /   /  _/_  __/ / / /
                  / /_/ / __/ / /    / /  / / / /_/ /
                 / __  / /___/ /____/ /  / / / __  /
                /_/ /_/_____/_____/___/ /_/ /_/ /_/
                           Helith - 0815
--------------------------------------------------------------------------------

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