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FreeBSD-SA-15:23.bind                                       Security Advisory
                                                          The FreeBSD Project

Topic:          BIND remote denial of service vulnerability

Category:       contrib
Module:         bind
Announced:      2015-09-02
Credits:        ISC
Affects:        FreeBSD 9.x
Corrected:      2015-09-02 20:06:46 UTC (stable/9, 9.3-STABLE)
                2015-09-02 20:07:03 UTC (releng/9.3, 9.3-RELEASE-p25)
CVE Name:       CVE-2015-5722

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://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.  The libdns
library is a library of DNS protocol support functions.

II.  Problem Description

Parsing a malformed DNSSEC key can cause a validating resolver to exit
due to a failed assertion in buffer.c.

III. Impact

A remote attacker can deliberately trigger the failed assertion which
will cause an affected server to terminate, by using a query that
requires a response from a zone containing a malformed key, resulting
in a denial of service condition.

Recursive servers are at greatest risk, however, an authoritative server
could also be affected, if an attacker controls a zone that the server
must query against to perform its zone service.

IV.  Workaround

No workaround is available, but hosts not running named(8) are not
vulnerable.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

The named service has to be restarted after the update.  A reboot is
recommended but not required.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

The named service has to be restarted after the update.  A reboot is
recommended but not required.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

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

[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-15:23/bind.patch
# fetch https://security.FreeBSD.org/patches/SA-15:23/bind.patch.asc
# gpg --verify bind.patch.asc

Please note that FreeBSD 9.3-STABLE is also affected by another issue
(CVE-2015-5986), and a different patch should be used.

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the named(8) daemon, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r287409
releng/9.3/                                                       r287410
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://kb.isc.org/article/AA-01287>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-5722>

CVE-2015-5986 is listed here for completeness and affects FreeBSD
9.3-STABLE but not FreeBSD 9.3-RELEASE:

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-5986>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-15:23.bind.asc>
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