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Category:   OS (UNIX)  >   NetBSD Vendors:   NetBSD
NetBSD IPv6 Neighbor Discovery Protocol Spoofing Bug Lets Remote Users Modify Routing Data in Certain Cases
SecurityTracker Alert ID:  1021109
SecurityTracker URL:
CVE Reference:   CVE-2008-2476   (Links to External Site)
Date:  Oct 27 2008
Impact:   Disclosure of system information, Disclosure of user information, Modification of system information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 3.0, 3.1, 4.0
Description:   A vulnerability was reported in the NetBSD IPv6 Neighbor Discovery Protocol. A remote user can modify routing data for a target router in certain cases.

A remote user on a physical network of an IPv6 router can spoof Neighbor Discovery messages to update routing information for a target router on a different physical network adjacent to the IPv6 router. The remote user can exploit this to deny service or access network traffic from the target router.

David Miles reported this vulnerability.

Impact:   A remote user can modify routing data for a target router in certain cases to deny service or redirect and access network traffic.
Solution:   The vendor has issued a source code fix.

The vendor's advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Authentication error

Message History:   None.

 Source Message Contents

Subject:  NetBSD Security Advisory 2008-013: IPv6 Neighbor Discovery Protocol

Hash: SHA1

		 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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