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Posted on 22 December 2016
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FreeBSD-SA-16:39.ntp Security Advisory
The FreeBSD Project
Topic: Multiple vulnerabilities of ntp
Category: contrib
Module: ntp
Announced: XXXX-XX-XX
Credits: Network Time Foundation
Affects: All supported versions of FreeBSD.
Corrected: 2016-11-22 16:22:51 UTC (stable/11, 11.0-STABLE)
2016-12-22 16:19:05 UTC (releng/11.0, 11.0-RELEASE-p6)
2016-11-22 16:23:20 UTC (stable/10, 10.3-STABLE)
2016-12-22 16:19:05 UTC (releng/10.3, 10.3-RELEASE-p15)
2016-12-22 16:19:05 UTC (releng/10.2, 10.2-RELEASE-p28)
2016-12-22 16:19:05 UTC (releng/10.1, 10.1-RELEASE-p45)
2016-11-22 16:23:46 UTC (stable/9, 9.3-STABLE)
2016-12-22 16:19:05 UTC (releng/9.3, 9.3-RELEASE-p53)
CVE Name: CVE-2016-7426, CVE-2016-7427, CVE-2016-7428, CVE-2016-7431,
CVE-2016-7433, CVE-2016-7434, CVE-2016-9310, CVE-2016-9311
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
The ntpd(8) daemon is an implementation of the Network Time Protocol (NTP)
used to synchronize the time of a computer system to a reference time
source.
Trap is a mechanism to collect NTP daemon information from remote.
II. Problem Description
Multiple vulnerabilities have been discovered in the NTP suite:
CVE-2016-9311: Trap crash, Reported by Matthew Van Gundy of Cisco ASIG.
CVE-2016-9310: Mode 6 unauthenticated trap information disclosure and DDoS
vector. Reported by Matthew Van Gundy of Cisco ASIG.
CVE-2016-7427: Broadcast Mode Replay Prevention DoS. Reported by
Matthew Van Gundy of Cisco ASIG.
CVE-2016-7428: Broadcast Mode Poll Interval Enforcement DoS. Reported by
Matthew Van Gundy of Cisco ASIG.
CVE-2016-7431: Regression: 010-origin: Zero Origin Timestamp Bypass.
Reported by Sharon Goldberg and Aanchal Malhotra of Boston University.
CVE-2016-7434: Null pointer dereference in _IO_str_init_static_internal().
Reported by Magnus Stubman.
CVE-2016-7426: Client rate limiting and server responses. Reported by
Miroslav Lichvar of Red Hat.
CVE-2016-7433: Reboot sync calculation problem. Reported independently
by Brian Utterback of Oracle, and by Sharon Goldberg and Aanchal Malhotra
of Boston University.
III. Impact
A remote attacker who can send a specially crafted packet to cause a
NULL pointer dereference that will crash ntpd, resulting in a Denial of
Service. [CVE-2016-9311]
An exploitable configuration modification vulnerability exists in the
control mode (mode 6) functionality of ntpd. If, against long-standing
BCP recommendations, "restrict default noquery ..." is not specified,
a specially crafted control mode packet can set ntpd traps, providing
information disclosure and DDoS amplification, and unset ntpd traps,
disabling legitimate monitoring by an attacker from remote. [CVE-2016-9310]
An attacker with access to the NTP broadcast domain can periodically
inject specially crafted broadcast mode NTP packets into the broadcast
domain which, while being logged by ntpd, can cause ntpd to reject
broadcast mode packets from legitimate NTP broadcast servers.
[CVE-2016-7427]
An attacker with access to the NTP broadcast domain can send specially
crafted broadcast mode NTP packets to the broadcast domain which, while
being logged by ntpd, will cause ntpd to reject broadcast mode packets
from legitimate NTP broadcast servers. [CVE-2016-7428]
Origin timestamp problems were fixed in ntp 4.2.8p6. However, subsequent
timestamp validation checks introduced a regression in the handling of
some Zero origin timestamp checks. [CVE-2016-7431]
If ntpd is configured to allow mrulist query requests from a server
that sends a crafted malicious packet, ntpd will crash on receipt of
that crafted malicious mrulist query packet. [CVE-2016-7434]
An attacker who knows the sources (e.g., from an IPv4 refid in server
response) and knows the system is (mis)configured in this way can
periodically send packets with spoofed source address to keep the rate
limiting activated and prevent ntpd from accepting valid responses
from its sources. [CVE-2016-7426]
Ntp Bug 2085 described a condition where the root delay was included
twice, causing the jitter value to be higher than expected. Due to
a misinterpretation of a small-print variable in The Book, the fix
for this problem was incorrect, resulting in a root distance that did
not include the peer dispersion. The calculations and formulas have
been reviewed and reconciled, and the code has been updated accordingly.
[CVE-2016-7433]
IV. Workaround
No workaround is available, but systems not running ntpd(8) are not
affected. Network administrators are advised to implement BCP-38,
which helps to reduce the risk associated with these attacks.
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 ntpd 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 ntpd 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 11.0]
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-11.0.patch
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-11.0.patch.asc
# gpg --verify ntp-11.0.patch.asc
[FreeBSD 10.x]
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-10.x.patch
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-10.x.patch.asc
# gpg --verify ntp-10.x.patch.asc
[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-9.3.patch
# fetch https://security.FreeBSD.org/patches/SA-16:39/ntp-9.3.patch.asc
# gpg --verify ntp-9.3.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 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/9/ r309009
releng/9.3/ r310419
stable/10/ r309008
releng/10.1/ r310419
releng/10.2/ r310419
releng/10.3/ r310419
stable/11/ r309007
releng/11.0/ r310419
- -------------------------------------------------------------------------
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:http://support.ntp.org/bin/view/Main/SecurityNotice#November_2016_ntp_4_2_8p9_NTP_Se>
<URL:https://www.kb.cert.org/vuls/id/633847>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7426>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7427>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7428>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7431>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7433>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-7434>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-9310>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-9311>
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:39.ntp.asc>
