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[NetBSD] Schwachstelle in der IPv6 Neighbor Discovery Implementierung - NetBSD-SA2008-013
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Liebe Kolleginnen und Kollegen,
soeben erreichte uns nachfolgende Warnung des NetBSD Security
Officers.Wir geben diese Informationen unveraendert an Sie weiter.
CVE-2008-2476 - IPv6 Stack akzeptiert Neigbor Solicitation Nachrichten
von anderen Layer 2 Segmenten
IPv6 Systeme verwenden das Neighbor Discovery Protocol, welches auf
ICMPv6 Nachrichten (Type 133 - 136) basiert, um die Link Layer Adresse
(OSI Layer 2) eines anderen Systems zu bestimmten (vgl. ARP). Das
Protokoll wird ebenfalls dazu benutzt, Router im lokalen Layer 2
Segment zu finden.
Der FreeBSD IPv6 Stack ueberprueft den Absender von Neighbor
Solicitation Nachrichten (ICMPv6 Type 135) nicht und akzeptiert
deshalb auch Nachrichten deren Absender sich in einem anderen Layer 2
Segment befindet.
Ein Angreifer auf einem anderen Layer 2 Segment kann diese
Schwachstelle dazu ausnutzen, IPv6 Netzwerkverkehr zu sich oder einem
anderen System umzuleiten indem er entsprechend aufgebaute Neighbor
Solicitation Pakete an das angegriffene System sendet. Dies kann u.a.
zu einem Denial of Service Angriff missbraucht werden oder Zugriff auf
evtl. vertrauliche Daten aus dem Netzwerkverkehr ermoeglichen.
Betroffen sind die folgenden Software Pakete und Plattformen:
NetBSD Versionen vor den folgenden Escheinungsdaten
NetBSD-current: July 31, 2008
NetBSD-4-0 branch: October 03, 2008
NetBSD-4 branch: October 03, 2008
NetBSD-3-1 branch: October 03, 2008
NetBSD-3-0 branch: October 03, 2008
NetBSD-3 branch: October 03, 2008
Vom Hersteller werden ueberarbeitete Pakete zur Verfuegung gestellt.
Hersteller Advisory:
ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2008-013.txt.asc
(c) der deutschen Zusammenfassung bei DFN-CERT Services GmbH; die
Verbreitung, auch auszugsweise, ist nur unter Hinweis auf den Urheber,
DFN-CERT Services GmbH, und nur zu nicht kommerziellen Zwecken
gestattet.
Mit freundlichen Gruessen,
Klaus Moeller, DFN-CERT
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NetBSD Security Advisory 2008-013
=================================
Topic: IPv6 Neighbor Discovery Protocol
Version: NetBSD-current: affected
NetBSD 4.0.*: not affected
NetBSD 4.0: affected
NetBSD 3.1.*: affected
NetBSD 3.1: affected
NetBSD 3.0.*: affected
NetBSD 3.0: affected
Severity: Denial of service
Fixed: NetBSD-current: July 31, 2008
NetBSD-4-0 branch: October 03, 2008
(4.0.1 includes the fix)
NetBSD-4 branch: October 03, 2008
(4.1 will include the fix)
NetBSD-3-1 branch: October 03, 2008
(3.1.2 will include the fix)
NetBSD-3-0 branch: October 03, 2008
(3.0.4 will include the fix)
NetBSD-3 branch: October 03, 2008
(3.2 will include the fix)
Abstract
========
An attacker may be able to forge IPv6 routing entries to intercept network
traffic or cause a denial of service attack.
This vulnerability has been assigned CVE-2008-2476 and CERT
Vulnerability Note VU#472363.
Technical Details
=================
An attacker on a local network (i.e. the messages will not be forwarded by
routers) can send a ICMPv6 neighbor solicitation message to a router which
will result in a modification of the victims routing information. It may be
then possible for the attacker intercept network traffic or cause a denial
of service.
Solutions and Workarounds
=========================
Only kernels compiled with the following option are vulnerable to this issue:
options INET6
As a temporary workaround recompile the kernel with the above option
commented out. The default NetBSD GENERIC kernels have this
option enabled.
In addition to this the following work arounds may also be used:
* Use application level encryption (e.g. SSH, HTTPS) to protect sensitive
network traffic.
* Use network firewalls to block any malicious ICMPv6 neighbor solicitation
messages.
For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
The fixed source may be obtained from the NetBSD CVS repository.
The following instructions briefly summarise how to upgrade your
kernel. In these instructions, replace:
ARCH with your architecture (from uname -m), and
KERNCONF with the name of your kernel configuration file.
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update sys/netinet6/nd6_nbr.c sys/netinet6/in6.c \
sys/netinet6/in6_var.h
# ./build.sh kernel=KERNCONF
# mv /netbsd /netbsd.old
# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd
# shutdown -r now
For more information on how to do this, see:
http://www.NetBSD.org/guide/en/chap-kernel.html
Thanks To
=========
Matt Thomas for the fix.
David Miles is credited with discovering this issue.
Revision History
================
2008-10-27 Initial release
More Information
================
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2008-013.txt.asc
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.
Copyright 2008, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2008-013.txt,v 1.3 2008/10/27 19:47:21 adrianp Exp $
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- --
Dipl. Inform. Klaus Moeller (Incident Response Team)
Phone: +49 40 808077-555, Fax: +49 40 808077-556
DFN-CERT Services GmbH, https://www.dfn-cert.de, Phone +49 40 808077-555
Sitz / Register: Hamburg, AG Hamburg, HRB 88805, Ust-IdNr.: DE 232129737
Sachsenstrase 5, 20097 Hamburg/Germany, CEO: Dr. Klaus-Peter Kossakowski
Automatische Warnmeldungen https://www.cert.dfn.de/autowarn
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