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CVE-2016-9312

Published: Jan 13, 2017Updated: May 13, 2026 Sources: CVE List NVDCWE-399
7.5HIGH
NVD MITRE
EPSS Score
31.2%
Top 1.8%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

ntpd in NTP before 4.2.8p9, when running on Windows, allows remote attackers to cause a denial of service via a large UDP packet.

In plain language

AI Worth attention

CVE-2016-9312 is a Windows-only bug in the NTP time server (ntpd) that can let someone on the network knock it offline using a very large UDP packet; a typical small business should worry if your NTP server is reachable from the internet or shared networks.

Executive summary

In ntpd (NTP) on Windows before 4.2.8p9, an attacker can trigger a denial of service by sending an oversized UDP packet that overwhelms the service (availability impact; remote, no authentication stated in the findings).

If affected, business impact
NTP service outageTime sync disruptionBusiness operations instabilityPotential secondary outages

What to do now

  1. Check whether you run an NTP server using ntpd on Windows, and whether UDP/123 is reachable from the internet or other untrusted networks.
  2. Identify your installed NTP version and confirm it is earlier than 4.2.8p9.
  3. Upgrade NTP on the affected Windows machines to 4.2.8p9 or later.
  4. If you cannot upgrade right now, restrict access to the NTP service (UDP/123) to only trusted internal IPs / networks per the available NTP workaround guidance.
  5. After changes, monitor for ntpd crashes or repeated service failures and verify that clients can still sync time.
Patch / advisory Some work to apply

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-399

Affected Products

ntp
oss-projectaka ntp daemon
ntpOn-prem
Networking Infrastructure / dns-dhcp-ntp
and 1 more affected products View all →

Exploitability

Official Patch Available
Workaround Available
Is your org exposed to CVE-2016-9312?We can run the check for you — a free external exposure review, no install. Check my exposure

References

http://support.ntp.org/bin/view/Main/SecurityNotice#Recent_Vulnerabilities
support.ntp.org
http://nwtime.org/ntp428p9_release/
nwtime.org
https://www.kb.cert.org/vuls/id/633847
kb.cert.org
and 4 more references View all →

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