OpenBSD 4.3 up to 4.5: PF null pointer dereference - remote DoS

2009.08.12
Credit: rembrandt
Risk: High
Local: No
Remote: Yes
CWE: CWE-399


CVSS Base Score: 7.8/10
Impact Subscore: 6.9/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: None
Integrity impact: None
Availability impact: Complete

_ _ _____ _ ___ _____ _ _ / / / / ____/ / / _/_ __/ / / / / /_/ / __/ / / / / / / / /_/ / / __ / /___/ /____/ / / / / __ / /_/ /_/_____/_____/___/ /_/ /_/ /_/ 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 : 8406 CVE : ISS X-Force: : BID : 34482 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

References:

http://www.vupen.com/english/advisories/2009/1015
http://www.openbsd.org/errata45.html#002_pf
http://www.openbsd.org/errata44.html#013_pf
http://www.openbsd.org/errata43.html#013_pf
ftp://ftp.openbsd.org/pub/OpenBSD/patches/4.3/common/013_pf.patch
http://xforce.iss.net/xforce/xfdb/49837
http://www.securityfocus.com/archive/1/502634
http://www.osvdb.org/53608
http://www.milw0rm.com/exploits/8581
http://www.milw0rm.com/exploits/8406
http://www.helith.net/txt/multiple_vendor-PF_null_pointer_dereference.txt
http://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2009-001.txt.asc


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