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From: "Geo"
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FreeBSD-SA-06:20.bind Security
Advisory
The FreeBSD
Project
Topic: Denial of Service in named(8)
Category: contrib
Module: bind
Announced: 2006-09-06
Credits: The Measurement Factory
Affects: FreeBSD 5.3 and later.
Corrected: 2006-09-06 21:18:26 UTC (RELENG_6, 6.1-STABLE)
2006-09-06 21:19:21 UTC (RELENG_6_1, 6.1-RELEASE-p6)
2006-09-06 21:20:08 UTC (RELENG_6_0, 6.0-RELEASE-p11)
2006-09-06 21:20:54 UTC (RELENG_5, 5.5-STABLE)
2006-09-06 21:21:50 UTC (RELENG_5_5, 5.5-RELEASE-p4)
2006-09-06 21:22:39 UTC (RELENG_5_4, 5.4-RELEASE-p18)
2006-09-06 21:23:16 UTC (RELENG_5_3, 5.3-RELEASE-p33)
CVE Name: CVE-2006-4095, CVE-2006-4096
For general information regarding FreeBSD Security Advisories, including
descriptions of the fields above, security branches, and the following
sections, please visit
http://security.freebsd.org/>.
I. Background
BIND 9 is an implementation of the Domain Name System (DNS) protocols. The
named(8) daemon is an Internet domain name server. DNS Security Extensions
(DNSSEC) are additional protocol options that add authentication and
integrity to the DNS protocols.
II. Problem Description
For a recursive DNS server, a remote attacker sending enough recursive
queries for the replies to arrive after all the interested clients have
left the recursion queue will trigger an INSIST failure in the named(8)
daemon. Also for a a recursive DNS server, an assertion failure can occour
when processing a query whose reply will contain more than one SIG(covered)
RRset.
For an authoritative DNS server serving a RFC 2535 DNSSEC zone which is
queried for the SIG records where there are multiple SIG(covered) RRsets
(e.g. a zone apex), named(8) will trigger an assertion failure when it
tries to construct the response.
III. Impact
An attacker who can perform recursive lookups on a DNS server and is able
to send a sufficiently large number of recursive queries, or is able to get
the DNS server to return more than one SIG(covered) RRsets can stop the
functionality of the DNS service.
An attacker querying an authoritative DNS server serving a RFC 2535 DNSSEC
zone may be able to crash the DNS server.
All of the above issues will result in a Denial of Service situation.
IV. Workaround
A possible workaround is to only allow trusted clients to perform recursive queries.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 5-STABLE, or 6-STABLE, or to the
RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, or RELENG_5_3 security
branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 5.3, 5.4, 5.5,
6.0, and 6.1 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-06:20/bind.patch
# fetch http://security.FreeBSD.org/patches/SA-06:20/bind.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/bind
# make obj && make depend && make && make install
# cd /usr/src/usr.sbin/named
# make obj && make depend && make && make install
c) Restart the named application:
# /etc/rc.d/named restart
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_5
src/contrib/bind9/bin/named/query.c 1.1.1.1.2.3
src/contrib/bind9/lib/dns/resolver.c 1.1.1.1.2.5
RELENG_5_5
src/UPDATING 1.342.2.35.2.4
src/sys/conf/newvers.sh 1.62.2.21.2.6
src/contrib/bind9/bin/named/query.c 1.1.1.1.2.2.2.1
src/contrib/bind9/lib/dns/resolver.c 1.1.1.1.2.4.2.1
RELENG_5_4
src/UPDATING 1.342.2.24.2.27
src/sys/conf/newvers.sh 1.62.2.18.2.23
src/contrib/bind9/bin/named/query.c 1.1.1.1.2.1.4.1
src/contrib/bind9/lib/dns/resolver.c 1.1.1.1.2.2.2.1
RELENG_5_3
src/UPDATING 1.342.2.13.2.36
src/sys/conf/newvers.sh 1.62.2.15.2.38
src/contrib/bind9/bin/named/query.c 1.1.1.1.2.1.2.1
src/contrib/bind9/lib/dns/resolver.c 1.1.1.1.2.1.2.1
RELENG_6
src/contrib/bind9/bin/named/query.c 1.1.1.1.4.2
src/contrib/bind9/lib/dns/resolver.c 1.1.1.2.2.3
RELENG_6_1
src/UPDATING 1.416.2.22.2.8
src/sys/conf/newvers.sh 1.69.2.11.2.8
src/contrib/bind9/bin/named/query.c 1.1.1.1.4.1.2.1
src/contrib/bind9/lib/dns/resolver.c 1.1.1.2.2.2.2.1
RELENG_6_0
src/UPDATING 1.416.2.3.2.16
src/sys/conf/newvers.sh 1.69.2.8.2.12
src/contrib/bind9/bin/named/query.c 1.1.1.1.6.1
src/contrib/bind9/lib/dns/resolver.c 1.1.1.2.2.1.2.1
- -------------------------------------------------------------------------
VII. References
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4095
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4096
http://www.kb.cert.org/vuls/id/697164
http://www.kb.cert.org/vuls/id/915404
http://www.niscc.gov.uk/niscc/docs/re-20060905-00590.pdf?lang=en
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:20.bind.asc
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