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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Moderate: ntp security update
Advisory ID:       RHSA-2016:1552-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2016-1552.html
Issue date:        2016-08-03
CVE Names:         CVE-2015-7979 CVE-2016-1547 CVE-2016-1548 
                   CVE-2016-1550 CVE-2016-2518 
=====================================================================

1. Summary:

An update for ntp is now available for Red Hat Enterprise Linux 6.7
Extended Update Support.

Red Hat Product Security has rated this update as having a security impact
of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available for each vulnerability from
the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux HPC Node EUS (v. 6.7) - x86_64
Red Hat Enterprise Linux HPC Node Optional EUS (v. 6.7) - noarch, x86_64
Red Hat Enterprise Linux Server EUS (v. 6.7) - i386, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional EUS (v. 6.7) - i386, noarch, ppc64, s390x, x86_64

3. Description:

The Network Time Protocol (NTP) is used to synchronize a computer's time
with another referenced time source. These packages include the ntpd
service which continuously adjusts system time and utilities used to query
and configure the ntpd service.

Security Fix(es):

* It was found that when NTP was configured in broadcast mode, a remote
attacker could broadcast packets with bad authentication to all clients.
The clients, upon receiving the malformed packets, would break the
association with the broadcast server, causing them to become out of sync
over a longer period of time. (CVE-2015-7979)

* A denial of service flaw was found in the way NTP handled preemptable
client associations. A remote attacker could send several crypto NAK
packets to a victim client, each with a spoofed source address of an
existing associated peer, preventing that client from synchronizing its
time. (CVE-2016-1547)

* It was found that an ntpd client could be forced to change from basic
client/server mode to the interleaved symmetric mode. A remote attacker
could use a spoofed packet that, when processed by an ntpd client, would
cause that client to reject all future legitimate server responses,
effectively disabling time synchronization on that client. (CVE-2016-1548)

* A flaw was found in the way NTP's libntp performed message
authentication. An attacker able to observe the timing of the comparison
function used in packet authentication could potentially use this flaw to
recover the message digest. (CVE-2016-1550)

* An out-of-bounds access flaw was found in the way ntpd processed certain
packets. An authenticated attacker could use a crafted packet to create a
peer association with hmode of 7 and larger, which could potentially
(although highly unlikely) cause ntpd to crash. (CVE-2016-2518)

The CVE-2016-1548 issue was discovered by Miroslav Lichvar (Red Hat).

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing this update, the ntpd daemon will restart automatically.

5. Bugs fixed (https://bugzilla.redhat.com/):

1300271 - CVE-2015-7979 ntp: off-path denial of service on authenticated broadcast mode
1331461 - CVE-2016-1547 ntp: crypto-NAK preemptable association denial of service
1331462 - CVE-2016-1548 ntp: ntpd switching to interleaved mode with spoofed packets
1331464 - CVE-2016-1550 ntp: libntp message digest disclosure
1331468 - CVE-2016-2518 ntp: out-of-bounds references on crafted packet

6. Package List:

Red Hat Enterprise Linux HPC Node EUS (v. 6.7):

Source:
ntp-4.2.6p5-5.el6_7.5.src.rpm

x86_64:
ntp-4.2.6p5-5.el6_7.5.x86_64.rpm
ntp-debuginfo-4.2.6p5-5.el6_7.5.x86_64.rpm
ntpdate-4.2.6p5-5.el6_7.5.x86_64.rpm

Red Hat Enterprise Linux HPC Node Optional EUS (v. 6.7):

noarch:
ntp-doc-4.2.6p5-5.el6_7.5.noarch.rpm

x86_64:
ntp-debuginfo-4.2.6p5-5.el6_7.5.x86_64.rpm
ntp-perl-4.2.6p5-5.el6_7.5.x86_64.rpm

Red Hat Enterprise Linux Server EUS (v. 6.7):

Source:
ntp-4.2.6p5-5.el6_7.5.src.rpm

i386:
ntp-4.2.6p5-5.el6_7.5.i686.rpm
ntp-debuginfo-4.2.6p5-5.el6_7.5.i686.rpm
ntpdate-4.2.6p5-5.el6_7.5.i686.rpm

ppc64:
ntp-4.2.6p5-5.el6_7.5.ppc64.rpm
ntp-debuginfo-4.2.6p5-5.el6_7.5.ppc64.rpm
ntpdate-4.2.6p5-5.el6_7.5.ppc64.rpm

s390x:
ntp-4.2.6p5-5.el6_7.5.s390x.rpm
ntp-debuginfo-4.2.6p5-5.el6_7.5.s390x.rpm
ntpdate-4.2.6p5-5.el6_7.5.s390x.rpm

x86_64:
ntp-4.2.6p5-5.el6_7.5.x86_64.rpm
ntp-debuginfo-4.2.6p5-5.el6_7.5.x86_64.rpm
ntpdate-4.2.6p5-5.el6_7.5.x86_64.rpm

Red Hat Enterprise Linux Server Optional EUS (v. 6.7):

i386:
ntp-debuginfo-4.2.6p5-5.el6_7.5.i686.rpm
ntp-perl-4.2.6p5-5.el6_7.5.i686.rpm

noarch:
ntp-doc-4.2.6p5-5.el6_7.5.noarch.rpm

ppc64:
ntp-debuginfo-4.2.6p5-5.el6_7.5.ppc64.rpm
ntp-perl-4.2.6p5-5.el6_7.5.ppc64.rpm

s390x:
ntp-debuginfo-4.2.6p5-5.el6_7.5.s390x.rpm
ntp-perl-4.2.6p5-5.el6_7.5.s390x.rpm

x86_64:
ntp-debuginfo-4.2.6p5-5.el6_7.5.x86_64.rpm
ntp-perl-4.2.6p5-5.el6_7.5.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2015-7979
https://access.redhat.com/security/cve/CVE-2016-1547
https://access.redhat.com/security/cve/CVE-2016-1548
https://access.redhat.com/security/cve/CVE-2016-1550
https://access.redhat.com/security/cve/CVE-2016-2518
https://access.redhat.com/security/updates/classification/#moderate

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2016 Red Hat, Inc.
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