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FreeBSD-SA-20:19.unbound Security Advisory
The FreeBSD Project
Topic: Multiple vulnerabilities in unbound
Category: contrib
Module: unbound
Announced: 2020-07-08
Affects: All supported versions of FreeBSD.
Corrected: 2020-05-24 16:47:27 UTC (stable/12, 12.1-STABLE)
2020-07-08 20:25:06 UTC (releng/12.1, 12.1-RELEASE-p7)
2020-05-24 11:47:27 UTC (stable/11, 11.4-STABLE)
2020-07-08 20:22:38 UTC (releng/11.4, 11.4-RELEASE-p1)
2020-07-08 20:20:59 UTC (releng/11.3, 11.3-RELEASE-p11)
CVE Name: CVE-2020-12662, CVE-2020-12663
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
Malformed answers from upstream name servers can send Unbound into an infinite
loop, resulting in denial of service. A malicious query can cause a traffic
amplification attack against third party authoritative nameservers.
III. Impact
Denial of service of the affected host, or of third parties via traffic
amplification.
IV. Workaround
No workaround is available. Systems not running Unbound are not affected.
V. Solution
Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.
Perform one of the following:
1) 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
2) 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 12.1]
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.12.1.patch
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.12.1.patch.asc
# gpg –verify unbound.12.1.patch.asc
[FreeBSD 11.4]
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.11.4.patch
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.11.4.patch.asc
# gpg –verify unbound.11.4.patch.asc
[FreeBSD 11.3]
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.11.3.patch
# fetch https://security.FreeBSD.org/patches/SA-20:19/unbound.11.3.patch.asc
# gpg –verify unbound.11.3.patch.asc
b) Apply the patch. Execute the following commands as root:
# cd /usr/src
# patch -p0 < /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 applicable daemons, or reboot the system.
VI. Correction details
The following list contains the correction revision numbers for each
affected branch.
Branch/path Revision
– ————————————————————————-
stable/12/ r361435
releng/12.1/ r363029
stable/11/ r361435
releng/11.4/ r363028
releng/11.3/ r363027
– ————————————————————————-
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://nlnetlabs.nl/downloads/unbound/CVE-2020-12662_2020-12663.txt>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-12662>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-12663>
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:19.unbound.asc>
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