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Category:   Application (Generic)  >   ntp Vendors:
(FreeBSD Issues Fix) ntp Bugs Let Remote Users Deny Service, Obtain Potentially Sensitive Information, and Bypass Access Controls in Certain Cases
SecurityTracker Alert ID:  1032036
SecurityTracker URL:
CVE Reference:   CVE-2014-9750   (Links to External Site)
Updated:  Nov 4 2015
Original Entry Date:  Apr 7 2015
Impact:   Denial of service via network, Disclosure of system information, Disclosure of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 4.2.8p1
Description:   Two vulnerabilities were reported in ntp. A remote user can cause denial of service conditions. A remote user can obtain potentially sensitive information. A remote user can bypass access controls in certain cases.

A remote user can send a specially crafted 'vallen' parameter value to trigger a validation flaw in 'ntp_crypto.c' and obtain potentially sensitive information or cause the target ntpd service to crash [CVE-2014-9750].

Stephen Roettger of the Google Security Team, Sebastian Krahmer of the SUSE Security Team, and Harlan Stenn of Network Time Foundation reported this vulnerability.

A remote user may be able to spoof the ::1 source address via IPv6 to bypass IPv6-based access controls [CVE-2014-9751]. Some operating systems are affected, including Apple OS X and Linux.

Stephen Roettger of the Google Security Team reported this vulnerability.

Impact:   A remote user can cause denial of service conditions.

A remote user can obtain potentially sensitive information.

A remote user can bypass access controls in certain cases.

Solution:   FreeBSD has issued a fix for CVE-2014-9750.

[Editor's note: On November 4, 2015, FreeBSD issued a revised advisory to announce new patches to fix a regression error. Users that have applied the original fix should apply the new incremental fix.]

The FreeBSD advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Access control error
Underlying OS:  UNIX (FreeBSD)
Underlying OS Comments:  8.4, 9.3, 10.1

Message History:   This archive entry is a follow-up to the message listed below.
Feb 16 2015 ntp Bugs Let Remote Users Deny Service, Obtain Potentially Sensitive Information, and Bypass Access Controls in Certain Cases

 Source Message Contents

Subject:  FreeBSD Security Advisory FreeBSD-SA-15:07.ntp

Hash: SHA512

FreeBSD-SA-15:07.ntp                                        Security Advisory
                                                          The FreeBSD Project

Topic:          Multiple vulnerabilities of ntp

Category:       contrib
Module:         ntp
Announced:      2015-04-07
Credits:        Network Time Foundation
Affects:        All supported versions of FreeBSD.
Corrected:      2015-04-07 20:20:24 UTC (stable/10, 10.1-STABLE)
                2015-04-07 20:21:01 UTC (releng/10.1, 10.1-RELEASE-p9)
                2015-04-07 20:20:44 UTC (stable/9, 9.3-STABLE)
                2015-04-07 20:21:23 UTC (releng/9.3, 9.3-RELEASE-p13)
                2015-04-07 20:20:44 UTC (stable/8, 8.4-STABLE)
                2015-04-07 20:21:23 UTC (releng/8.4, 8.4-RELEASE-p27)
CVE Name:       CVE-2014-9297, CVE-2015-1798, CVE-2015-1799

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:>.

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

II.  Problem Description

The vallen packet value is not validated in several code paths in
ntp_crypto.c. [CVE-2014-9297]

When ntpd(8) is configured to use a symmetric key to authenticate a remote
NTP server/peer, it checks if the NTP message authentication code (MAC)
in received packets is valid, but not that there actually is any MAC
included, and packets without a MAC are accepted as if they had a valid
MAC. [CVE-2015-1798]

NTP state variables are updated prior to validating the received packets.

III. Impact

A remote attacker who can send specifically crafted packets may be able
to reveal memory contents of ntpd(8) or cause it to crash, when ntpd(8)
is configured to use autokey. [CVE-2014-9297]

A man-in-the-middle (MITM) attacker can send specially forged packets
that would be accepted by the client/peer without having to know the
symmetric key. [CVE-2015-1798]

An attacker knowing that NTP hosts A and B are peering with each other
(symmetric association) can periodically send a specially crafted or
replayed packet which will break the synchronization between the two
peers due to transmit timestamp mismatch, preventing the two nodes from
synchronizing with each other, even when authentication is enabled.

IV.  Workaround

No workaround is available, but systems not running ntpd(8) are not

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.

# fetch
# fetch
# gpg --verify ntp.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:>.

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/8/                                                         r281231
releng/8.4/                                                       r281233
stable/9/                                                         r281231
releng/9.3/                                                       r281233
stable/10/                                                        r281230
releng/10.1/                                                      r281232
- -------------------------------------------------------------------------

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://

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


VII. References




The latest revision of this advisory is available at
Version: GnuPG v2.1.2 (FreeBSD)

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