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NTP: Traffic amplification


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 201401-08 /
Release Date January 16, 2014
Latest Revision January 16, 2014: 1
Impact normal
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
net-misc/ntp < 4.2.6_p5-r10 >= 4.2.6_p5-r10 All supported architectures

Related bugreports: #496776


NTP can be abused to amplify Denial of Service attack traffic.

2.  Impact Information


NTP is a protocol designed to synchronize the clocks of computers over a network. The net-misc/ntp package contains the official reference implementation by the NTP Project.


ntpd is susceptible to a reflected Denial of Service attack. Please review the CVE identifiers and references below for details.


An unauthenticated remote attacker may conduct a distributed reflective Denial of Service attack on another user via a vulnerable NTP server.

3.  Resolution Information


We modified the default ntp configuration in =net-misc/ntp-4.2.6_p5-r10 and added “noquery” to the default restriction which disallows anyone to query the ntpd status, including “monlist”.

If you use a non-default configuration, and provide a ntp service to untrusted networks, we highly recommend you to revise your configuration to disable mode 6 and 7 queries for any untrusted (public) network.

You can always enable these queries for specific trusted networks. For more details please see the “Access Control Support” chapter in the ntp.conf(5) man page.


All NTP users should upgrade to the latest version:

Code Listing 3.1: Resolution

  # emerge --sync
  # emerge --ask --oneshot --verbose ">=net-misc/ntp-4.2.6_p5-r10"

Note that the updated package contains a modified default configuration only. You may need to modify your configuration further.

4.  References


Page updated January 16, 2014

Summary: This is a Gentoo Linux Security Advisory

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