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FreeBSD-SA-14:30.unbound Security Advisory
The FreeBSD Project

Topic: unbound remote denial of service vulnerability

Category: contrib
Module: unbound
Announced: 2014-12-17
Affects: FreeBSD 10.0-RELEASE and later
Credits: Florian Maury (ANSSI)
Corrected: 2014-12-17 06:58:00 UTC (stable/10, 10.1-STABLE)
2014-12-17 06:59:47 UTC (releng/10.1, 10.1-RELEASE-p2)
2014-12-17 06:59:47 UTC (releng/10.0, 10.0-RELEASE-p14)
CVE Name: CVE-2014-8602

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

Unbound is a validating, recursive, and caching DNS resolver.

II. Problem Description

By causing queries to be made against a maliciously-constructed zone or
against a malicious DNS server, an attacker who is able to cause
specific queries to be sent to a nameserver can trick unbound(8) resolver
into following an endless series of delegations, which consumes a lot of
resources.

III. Impact

Unbound will spend a lot of resources on this query, and this will impact
unbound’s CPU and network resources. Unbound may therefore lose some
ability or timelines for the service of customer queries (a denial of
service). Unbound will continue to respond normally for cached queries.

IV. Workaround

No workaround is available, but hosts not running unbound(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.

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

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 10.x]
# fetch https://security.FreeBSD.org/patches/SA-14:30/unbound.patch
# fetch https://security.FreeBSD.org/patches/SA-14:30/unbound.patch.asc
# gpg –verify unbound.patch.asc

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 unbound(8) daemons, or reboot the system.

VI. Correction details

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

Branch/path Revision
– ————————————————————————-
stable/10/ r275853
releng/10.0/ r275854
releng/10.1/ r275854
– ————————————————————————-

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://unbound.net/downloads/CVE-2014-8602.txt>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-8602>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-14:30.unbound.asc>
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