FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

Type securityvulns
Reporter Securityvulns
Modified 2007-04-27T00:00:00



============================================================================= FreeBSD-SA-07:03.ipv6 Security Advisory The FreeBSD Project

Topic: IPv6 Routing Header 0 is dangerous

Category: core Module: ipv6 Announced: 2007-04-26 Credits: Philippe Biondi, Arnaud Ebalard, Jun-ichiro itojun Hagino Affects: All FreeBSD releases. Corrected: 2007-04-24 11:42:42 UTC (RELENG_6, 6.2-STABLE) 2007-04-26 23:42:23 UTC (RELENG_6_2, 6.2-RELEASE-p4) 2007-04-26 23:41:59 UTC (RELENG_6_1, 6.1-RELEASE-p16) 2007-04-24 11:44:23 UTC (RELENG_5, 5.5-STABLE) 2007-04-26 23:41:27 UTC (RELENG_5_5, 5.5-RELEASE-p12) CVE Name: CVE-2007-2242

I. Background

IPv6 provides a routing header option which allows a packet sender to indicate how the packet should be routed, overriding the routing knowledge present in a network. This functionality is roughly equivalent to the "source routing" option in IPv4. All nodes in an IPv6 network -- both routers and hosts -- are required by RFC 2640 to process such headers.

II. Problem Description

There is no mechanism for preventing IPv6 routing headers from being used to route packets over the same link(s) many times.

III. Impact

An attacker can "amplify" a denial of service attack against a link between two vulnerable hosts; that is, by sending a small volume of traffic the attacker can consume a much larger amount of bandwidth between the two vulnerable hosts.

An attacker can use vulnerable hosts to "concentrate" a denial of service attack against a victim host or network; that is, a set of packets sent over a period of 30 seconds or more could be constructed such that they all arrive at the victim within a period of 1 second or less.

Other attacks may also be possible.

IV. Workaround

No workaround is available.

V. Solution

NOTE WELL: The solution described below causes IPv6 type 0 routing headers to be ignored. Support for IPv6 type 0 routing headers can be re-enabled if required by setting the newly added net.inet6.ip6.rthdr0_allowed sysctl to a non-zero value.

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE, or 6-STABLE, or to the RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 5.5, 6.1, and 6.2 systems.

a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility.



b) Apply the patch.

cd /usr/src

patch < /path/to/patch

c) Recompile your kernel as described in <URL:> and reboot the system.

VI. Correction details

The following list contains the revision numbers of each file that was corrected in FreeBSD.

Branch Revision Path

RELENG_5 src/sys/netinet6/in6.h src/sys/netinet6/in6_proto.c src/sys/netinet6/route6.c RELENG_5_5 src/UPDATING 1.342. src/sys/conf/ src/sys/netinet6/in6.h src/sys/netinet6/in6_proto.c src/sys/netinet6/route6.c RELENG_6 src/sys/netinet6/in6.h src/sys/netinet6/in6_proto.c src/sys/netinet6/route6.c RELENG_6_2 src/UPDATING 1.416. src/sys/conf/ src/sys/netinet6/in6.h src/sys/netinet6/in6_proto.c src/sys/netinet6/route6.c RELENG_6_1 src/UPDATING 1.416. src/sys/conf/ src/sys/netinet6/in6.h src/sys/netinet6/in6_proto.c src/sys/netinet6/route6.c

VII. References

The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD)

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