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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE glsa SYSTEM "http://www.gentoo.org/dtd/glsa.dtd">
<glsa id="200708-13">
<title>BIND: Weak random number generation</title>
<synopsis>
The ISC BIND random number generator uses a weak algorithm, making it
easier to guess the next query ID and perform a DNS cache poisoning attack.
</synopsis>
<product type="ebuild">bind</product>
<announced>August 18, 2007</announced>
<revised>August 18, 2007: 01</revised>
<bug>186556</bug>
<access>remote</access>
<affected>
<package name="net-dns/bind" auto="yes" arch="*">
<unaffected range="ge">9.4.1_p1</unaffected>
<vulnerable range="lt">9.4.1_p1</vulnerable>
</package>
</affected>
<background>
<p>
ISC BIND is the Internet Systems Consortium implementation of the
Domain Name System (DNS) protocol.
</p>
</background>
<description>
<p>
Amit Klein from Trusteer reported that the random number generator of
ISC BIND leads, half the time, to predictable (1 chance to 8) query IDs
in the resolver routine or in zone transfer queries (CVE-2007-2926).
Additionally, the default configuration file has been strengthen with
respect to the allow-recursion{} and the allow-query{} options
(CVE-2007-2925).
</p>
</description>
<impact type="normal">
<p>
A remote attacker can use this weakness by sending queries for a domain
he handles to a resolver (directly to a recursive server, or through
another process like an email processing) and then observing the
resulting IDs of the iterative queries. The attacker will half the time
be able to guess the next query ID, then perform cache poisoning by
answering with those guessed IDs, while spoofing the UDP source address
of the reply. Furthermore, with empty allow-recursion{} and
allow-query{} options, the default configuration allowed anybody to
make recursive queries and query the cache.
</p>
</impact>
<workaround>
<p>
There is no known workaround at this time for the random generator
weakness. The allow-recursion{} and allow-query{} options should be set
to trusted hosts only in /etc/bind/named.conf, thus preventing several
security risks.
</p>
</workaround>
<resolution>
<p>
All ISC BIND users should upgrade to the latest version:
</p>
<code>
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-dns/bind-9.4.1_p1"</code>
</resolution>
<references>
<uri link="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2925">CVE-2007-2925</uri>
<uri link="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2926">CVE-2007-2926</uri>
</references>
<metadata tag="requester" timestamp="Sun, 05 Aug 2007 10:40:49 +0000">
aetius
</metadata>
<metadata tag="submitter" timestamp="Mon, 13 Aug 2007 23:06:16 +0000">
falco
</metadata>
<metadata tag="bugReady" timestamp="Tue, 14 Aug 2007 23:00:40 +0000">
falco
</metadata>
</glsa>
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