<?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>2007-08-18</announced>
  <revised count="01">2007-08-18</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 "&gt;=net-dns/bind-9.4.1_p1"</code>
  </resolution>
  <references>
    <uri link="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2925">CVE-2007-2925</uri>
    <uri link="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2926">CVE-2007-2926</uri>
  </references>
  <metadata tag="requester" timestamp="2007-08-05T10:40:49Z">
    aetius
  </metadata>
  <metadata tag="submitter" timestamp="2007-08-13T23:06:16Z">
    falco
  </metadata>
  <metadata tag="bugReady" timestamp="2007-08-14T23:00:40Z">
    falco
  </metadata>
</glsa>
