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NetBSD Security Advisory 2008-013: IPv6 Neighbor Discovery Protocol

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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)


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 

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 \
        # ./ 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:

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

Information about NetBSD and NetBSD security can be found at and

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 $

Version: GnuPG v1.4.9 (NetBSD)


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