NTP can be exploited to generate huge volumes of junk traffic which leads to DOS attack. Update your NTP service to ntp-4.2.8p9 which patches this Vulnerability.

What is NTP?

Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.  NTP is one of the oldest Internet protocols in current use.

NTP users are strongly recommended to take immediate action to ensure that their NTP servers are not being vulnerable DDoS (distributed denial-of-service) attacks.



NTF’s NTP Project -4.2.8p9, addresses:
  • 1 HIGH severity vulnerability that only affects Windows
  • 2 MEDIUM severity vulnerabilities
  • 2 MEDIUM/LOW severity vulnerabilities
  • 5 LOW severity vulnerabilities

For more details on Vulnerability Announcement refer NTP security advisory.NTP.org’s ntpd prior to version 4.2.8p9 contains multiple denial of service vulnerabilities.

CWE-476: NULL Pointer Dereference – CVE-2016-9311
CWE-400: Uncontrolled Resource Consumption (‘Resource Exhaustion’) – CVE-2016-9310
CWE-400: Uncontrolled Resource Consumption (‘Resource Exhaustion’) – CVE-2016-7427
CWE-400: Uncontrolled Resource Consumption (‘Resource Exhaustion’) – CVE-2016-7428
CWE-410: Insufficient Resource Pool – CVE-2016-9312
CWE-20: Improper Input Validation – CVE-2016-7431
CWE-20: Improper Input Validation – CVE-2016-7434
CWE-605: Multiple Binds to the Same Port – CVE-2016-7429
CWE-410: Insufficient Resource Pool – CVE-2016-7426
CWE-682: Incorrect Calculation – CVE-2016-7433

For more information, please see NTP.org’s security advisory.The CVSS score below is based on CVE-2016-9312.


A remote unauthenticated attacker may be able to perform a denial of service on ntpd.


Implement BCP-38

Use “restrict default noquery …” in your ntp.conf file. Only allow mode 6 queries from trusted networks and hosts.

Apply an update

Upgrade to 4.2.8p9, or later, from the NTP Project Download Page or the NTP Public Services Project Download Page.

Monitor ntpd

Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.


Gurubaran is a PKI Security Engineer. Certified Ethical Hacker, Penetration Tester, Security blogger, Co-Founder & Author of GBHackers On Security.

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