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Category:   Application (Generic)  >   ntp Vendors:   ntp.org
(FreeBSD Issues Fix) ntp Multiple Bugs Let Remote Users Cause the Target Service to Crash
SecurityTracker Alert ID:  1037524
SecurityTracker URL:  http://securitytracker.com/id/1037524
CVE Reference:   CVE-2016-7426, CVE-2016-7427, CVE-2016-7428, CVE-2016-7431, CVE-2016-7433, CVE-2016-7434, CVE-2016-9310, CVE-2016-9311   (Links to External Site)
Date:  Dec 22 2016
Impact:   Denial of service via network, Disclosure of system information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 4.2.8p9
Description:   Multiple vulnerabilities were reported in ntp. A remote user can cause the target service to crash.

On Windows-based systems with the trap service enabled, a remote user can send a specially crafted packet to trigger a null pointer dereference and cause the ntpd daemon to crash [CVE-2016-9311].

A remote user can send a specially crafted control mode packet to set and unset ntpd traps. As a result, a remote user can obtain potentially sensitive information, conduct denial of service amplification attacks, or cause monitoring to become disabled [CVE-2016-9310].

A remote user with access to the target NTP broadcast domain can inject specially crafted broadcast mode NTP packets into the NTP broadcast domain to exploit a flaw in the replay prevention function cause the target ntpd daemon to reject broadcast mode NTP packets from legitimate NTP broadcast servers [CVE-2016-7427].

A remote user with access to the target NTP broadcast domain can inject specially crafted broadcast mode NTP packets into the NTP broadcast domain to exploit a flaw in the broadcast mode poll interval enforcement function and cause the target ntpd daemon to reject broadcast mode NTP packets from legitimate NTP broadcast servers [CVE-2016-7428].

A remote user can send a specially crafted, large UDP packet to cause the target ntpd daemon to stop functioning [CVE-2016-9312]. Windows based systems are affected.

A regression error exists in the validation of zero origin timestamps [CVE-2016-7431].

On systems with ntpd configured to allow mrulist query requests from the remote user, a remote user can send a specially crafted mrulist query request packet to cause the target ntpd daemon to crash [CVE-2016-7434].

On systems with multiple interfaces on separate networks and where the operating system does not validate source addresses in received packets, a remote user can send a specially crafted packet to trigger an error in selecting the proper interface and temporarily prevent the target ntpd daemon from sending new requests [CVE-2016-7429].

On systems with ntpd configured with rate limiting for all associations, a remote user can send packets with specially crafted source addresses to keep the rate limiting function active and prevent the target ntpd daemon from accepting valid responses [CVE-2016-7426].

An error may occur in the calculation of root sync delay, causing the jitter value to be higher than expected [CVE-2016-7433].

Matthew Van Gundy of Cisco ASIG, Robert Pajak of ABB, Magnus Stubman, Miroslav Lichvar of Red Hat, Brian Utterback of Oracle, and Sharon Goldberg and Aanchal Malhotra of Boston University reported these vulnerabilities.

Impact:   A remote user can cause the target service to crash.

A remote user can obtain potentially sensitive information from the target system.

A remote user can conduct denial of service amplification attacks against other targets.

Solution:   FreeBSD has issued a fix for CVE-2016-7426, CVE-2016-7427, CVE-2016-7428, CVE-2016-7431, CVE-2016-7433, CVE-2016-7434, CVE-2016-9310, and CVE-2016-9311.

The FreeBSD advisory is available at:

https://security.FreeBSD.org/advisories/FreeBSD-SA-16:39.ntp.asc

Vendor URL:  security.FreeBSD.org/advisories/FreeBSD-SA-16:39.ntp.asc (Links to External Site)
Cause:   Access control error, Boundary error, Input validation error, State error
Underlying OS:  UNIX (FreeBSD)
Underlying OS Comments:  9.3, 10.1, 10.2, 10.3, 11.0

Message History:   This archive entry is a follow-up to the message listed below.
Nov 29 2016 ntp Multiple Bugs Let Remote Users Cause the Target Service to Crash



 Source Message Contents

Subject:  FreeBSD Security Advisory FreeBSD-SA-16:39.ntp

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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>
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