(Red Hat Issues Fix) ntp Multiple Bugs Let Remote Users Spoof Messages, Obtain Potentially Sensitive Information, Modify Time, and Deny Service
SecurityTracker Alert ID: 1036523|
SecurityTracker URL: http://securitytracker.com/id/1036523
CVE-2016-1547, CVE-2016-1548, CVE-2016-1550, CVE-2016-2518
(Links to External Site)
Date: Aug 3 2016
Denial of service via network, Disclosure of system information, Disclosure of user information, Modification of system information, Modification of user information|
Fix Available: Yes Vendor Confirmed: Yes |
Multiple vulnerabilities were reported in ntp. A remote or remote authenticated user can modify time on the target system. A remote user can cause denial of service conditions on the target system. A remote user can obtain potentially sensitive information on the target system.|
A remote user can send specially crafted crypto-NAK packets with a spoofed source address of an existing peer to trigger an error in 'ntp_proto.c' and cause the preemptable client association to be demobilized [CVE-2016-1547].
A remote user can send a spoofed packet with a specially crafted timestamp to cause the target ntpd client to reject future server responses from the spoofed server. As a result, the remote user can modify the time of the target client or cause denial of service conditions on the target client [CVE-2016-1548].
A remote authenticated peer can create an arbitrary number of ephemeral associations to modify the time on the target system [CVE-2016-1549].
A remote user can send a series of specially crafted messages to potentially recover the message digest key [CVE-2016-1550].
A remote user can send specially crafted spoofed packets to a target system that fails to implement martian packet filtering to modify the time on the target system [CVE-2016-1551].
A remote user with knowledge of the controlkey (for ntpq) or the requestkey (for ntpdc) can create a specially crafted session to cause ntpd to crash in certain cases [CVE-2016-2516].
A remote authenticated user with knowledge of the of the controlkey (for ntpq) or the requestkey (for ntpdc) can create a specially crafted session to prevent ntpd from processing authentication requests until the process is restarted [CVE-2016-2517].
A remote authenticated user can send a specially crafted packet to trigger an out-of-bounds memory reference error in the MATCH_ASSOC() function when creating a peer association with hmode > 7 [CVE-2016-2518].
A remote authenticated user can cause a specially crafted data value to be stored by ntpd and then cause ntpd to crash when attempting to read the value via ctl_getitem() [CVE-2016-2519].
Matt Street, Matthew Van Gundy, Stephen Gray, Jonathan Gardner, and others of Cisco ASIG, Yihan Lian (of the Cloud Security Team, Qihoo 360), Miroslav Lichvar of RedHat, Michael Tatarinov (NTP Project Developer Volunteer), and Loganaden Velvindron reported these vulnerabilities.
A remote or remote authenticated user can modify time on the target system.|
A remote user can cause denial of service conditions.
A remote user can obtain potentially sensitive information on the target system.
Red Hat has issued a fix for CVE-2016-1547, CVE-2016-1548, CVE-2016-1550, and CVE-2016-2518.|
The Red Hat advisory is available at:
Vendor URL: rhn.redhat.com/errata/RHSA-2016-1552.html (Links to External Site)
Access control error, Input validation error, State error|
|Underlying OS: Linux (Red Hat Enterprise)|
|Underlying OS Comments: 6.7|
This archive entry is a follow-up to the message listed below.|
Source Message Contents
Subject: [RHSA-2016:1552-01] Moderate: ntp security update|
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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
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
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.
* 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
* 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).
For details on how to apply this update, which includes the changes
described in this advisory, refer to:
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):
Red Hat Enterprise Linux HPC Node Optional EUS (v. 6.7):
Red Hat Enterprise Linux Server EUS (v. 6.7):
Red Hat Enterprise Linux Server Optional EUS (v. 6.7):
These packages are GPG signed by Red Hat for security. Our key and
details on how to verify the signature are available from
The Red Hat security contact is <email@example.com>. More contact
details at https://access.redhat.com/security/team/contact/
Copyright 2016 Red Hat, Inc.
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