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Vulnerability record · CVE-2016-2517 · published 30 January 2017

CVE-2016-2517: Ntp improper input validation vulnerability

Ntp · Ntp

NTP before 4.2.8p7 and 4.3.x before 4.3.92 allows remote attackers to cause a denial of service (prevent subsequent authentication) by leveraging knowledge of the controlkey or requestkey and sending a crafted packet to ntpd, which changes the value of trustedkey, controlkey, or requestkey. NOTE: this vulnerability exists because of a CVE-2016-2516 regression.

5.3 CVSS 3.0 Medium EPSS 8.8% · top 5.0% CWE-20 · Improper input validation
5.3CVSS 3.0 base score, v2 4.9
8.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
16References
17 Jun 2026Last modified by NVD

Description

NTP before 4.2.8p7 and 4.3.x before 4.3.92 allows remote attackers to cause a denial of service (prevent subsequent authentication) by leveraging knowledge of the controlkey or requestkey and sending a crafted packet to ntpd, which changes the value of trustedkey, controlkey, or requestkey. NOTE: this vulnerability exists because of a CVE-2016-2516 regression.

CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://support.ntp.org/bin/view/Main/NtpBug3010 Vendor Advisory
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html Third Party Advisory
http://www.securityfocus.com/bid/88189 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1035705
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://www.kb.cert.org/vuls/id/718152 Third Party AdvisoryUS Government Resource
http://support.ntp.org/bin/view/Main/NtpBug3010 Vendor Advisory
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html Third Party Advisory
http://www.securityfocus.com/bid/88189 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1035705
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://www.kb.cert.org/vuls/id/718152 Third Party AdvisoryUS Government Resource

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2018-12327Ntp out-of-bounds write vulnerabilityStack-based buffer overflow in ntpq and ntpdc of NTP version 4.2.8p11 allows an attacker to achieve code execution or escalate to higher privileges v…EPSS 28%9.8CVE-2018-7183Ntp out-of-bounds write vulnerabilityBuffer overflow in the decodearr function in ntpq in ntp 4.2.8p6 through 4.2.8p10 allows remote attackers to execute arbitrary code by leveraging an …EPSS 10%9.8CVE-2015-7705Ntp improper input validation vulnerabilityThe 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 impact via a large number of …EPSS 12%9.8CVE-2015-7853Ntp classic buffer overflow vulnerabilityThe 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 attackers to execute arbitrary code o…EPSS 12%9.8CVE-2015-7871ntpd Crypto-NAK packets bypass authenticationntpd in NTP 4.2.x before 4.2.8p4 and 4.3.x before 4.3.77 mishandles Crypto-NAK packets, allowing remote attackers to bypass authentication. Because N…EPSS 82%analysed8.8CVE-2015-7849Ntp use after free vulnerabilityUse-after-free vulnerability in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote authenticated users to possibly execute arbit…EPSS 17%8.8CVE-2015-7854Ntp classic buffer overflow vulnerabilityBuffer overflow in the password management functionality in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote authenticated users to ca…EPSS 15%8.8CVE-2017-6458Ntp memory buffer overflow vulnerabilityMultiple buffer overflows in the ctl_put* functions in NTP before 4.2.8p10 and 4.3.x before 4.3.94 allow remote authenticated users to have unspecifi…EPSS 6.5%

Source: NIST National Vulnerability Database (record CVE-2016-2517), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.