CVE-2016-1549

CVE-2016-1549 is a medium-severity vulnerability in Ntp with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-19.

Key facts

• Severity: Medium (CVSS 3.x base score 6.5)
• CVSS v2: 4.0
• EPSS exploit prediction: 3% (86th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-19
• Affected product: Ntp
• Published: 2017-01-06
• Last modified: 2026-06-17

Description

A malicious authenticated peer can create arbitrarily-many ephemeral associations in order to win the clock selection algorithm in ntpd in NTP 4.2.8p4 and earlier and NTPsec 3e160db8dc248a0bcb053b56a80167dc742d2b74 and a5fb34b9cc89b92a8fef2f459004865c93bb7f92 and modify a victim's clock.

Frequently asked questions

What is CVE-2016-1549?

A malicious authenticated peer can create arbitrarily-many ephemeral associations in order to win the clock selection algorithm in ntpd in NTP 4.2.8p4 and earlier and NTPsec 3e160db8dc248a0bcb053b56a80167dc742d2b74 and a5fb34b9cc89b92a8fef2f459004865c93bb7f92 and modify a victim's clock.

How severe is CVE-2016-1549?

CVE-2016-1549 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2016-1549 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-1549?

CVE-2016-1549 affects Ntp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2016-1549?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2016-1549 published?

CVE-2016-1549 was published on 2017-01-06 and last updated on 2026-06-17.

References

• http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
• http://www.securityfocus.com/bid/88200
• http://www.securitytracker.com/id/1035705
• http://www.talosintelligence.com/reports/TALOS-2016-0083/
• https://security.FreeBSD.org/advisories/FreeBSD-SA-16:16.ntp.asc
• https://security.gentoo.org/glsa/201607-15
• https://security.netapp.com/advisory/ntap-20171004-0002/
• https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03962en_us
• https://www.synology.com/support/security/Synology_SA_18_13

Affected products (1)

• cpe:2.3:a:ntp:ntp:4.2.8:p4:*:*:*:*:*:*

More vulnerabilities in Ntp

• CVE-2018-12327 — Critical (CVSS 9.8): Stack-based buffer overflow in ntpq and ntpdc of NTP version 4.2.8p11 allows an attacker to achieve code execution or…
• CVE-2018-7183 — Critical (CVSS 9.8): Buffer overflow in the decodearr function in ntpq in ntp 4.2.8p6 through 4.2.8p10 allows remote attackers to execute…
• CVE-2015-7871 — Critical (CVSS 9.8): Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass…
• CVE-2015-7853 — Critical (CVSS 9.8): The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote…
• CVE-2015-7705 — Critical (CVSS 9.8): The rate limiting feature in NTP 4.x before 4.2.8p4 and 4.3.x before 4.3.77 allows remote attackers to have unspecified…
• CVE-2015-7854 — High (CVSS 8.8): Buffer overflow in the password management functionality in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows…

All CVEs affecting Ntp →

Other CWE-19 vulnerabilities

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• CVE-2014-8822 — Critical (CVSS 10.0): IOHIDFamily in Apple OS X before 10.10.2 allows attackers to execute arbitrary code in a kernel context or cause a…
• CVE-2014-8817 — Critical (CVSS 10.0): coresymbolicationd in CoreSymbolication in Apple OS X before 10.10.2 does not verify that expected data types are…
• CVE-2014-4488 — Critical (CVSS 10.0): IOHIDFamily in Apple iOS before 8.1.3, Apple OS X before 10.10.2, and Apple TV before 7.0.3 does not properly validate…
• CVE-2014-7247 — Critical (CVSS 10.0): Unspecified vulnerability in JustSystems Ichitaro 2008 through 2011; Ichitaro Government 6, 7, 2008, 2009, and 2010;…
• CVE-1999-0226 — Critical (CVSS 10.0): Windows NT TCP/IP processes fragmented IP packets improperly, causing a denial of service.

Browse all CWE-19 vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 197.248.207.139 (ipv4-addr)
• 135.129.128.247 (ipv4-addr)
• 119.201.59.224 (ipv4-addr)
• 125.212.244.35 (ipv4-addr)
• 202.29.220.126 (ipv4-addr)
• 93.42.227.251 (ipv4-addr)
• 82.209.191.11 (ipv4-addr)
• 119.204.60.250 (ipv4-addr)