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CVE-2016-2516

21
FAUCET Score

CVE-2016-2516 is a denial-of-service vulnerability affecting NTP versions before 4.2.8p7 and 4.3.x before 4.3.92, specifically when mode7 is enabled. An authenticated remote attacker can trigger an ntpd abort by repeatedly using the same IP address within an unconfig directive. This vulnerability has a CVSS score of 5.3 (Medium), indicating a network-based attack with high impact on availability and high attack complexity. There is no evidence of active exploitation, and no public exploit code (Metasploit, Nuclei, ExploitDB) is available. Community discussion and media coverage are minimal, suggesting low current attention.

Impacted Technologies

VendorProductVersion(s)CPE
<= 4.2.8CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:*:p6:*:*:*:*:*:*
4.3.25CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.3.25:*:*:*:*:*:*:*
4.3.26CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.3.26:*:*:*:*:*:*:*
4.3.27CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.3.27:*:*:*:*:*:*:*
4.3.28CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.3.28:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.6
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
8.95%
Probability of exploitation in next 30 days
EPSS Percentile
94.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0895 is in the 97th percentile among its peer group of 1,425 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (2)

redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: ntp
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: ntp

Vendor Advisories (1)

redhatCVE-2016-2516Moderate

ntp: assertion failure in ntpd on duplicate IPs on unconfig directives

Apr 26, 2016

References

security.freebsd.org / advisories/FreeBSD-SA-16:16.ntp.asc
security.gentoo.org / glsa/201607-15
security.netapp.com / advisory/ntap-20171004-0002
support.ntp.org / bin/view/Main/NtpBug3011
Vendor Advisory
kb.cert.org / vuls/id/718152
Third Party AdvisoryUS Government Resource
debian.org / security/2016/dsa-3629
oracle.com / technetwork/topics/security/bulletinapr2016-2952098.html
Third Party Advisory
securityfocus.com / bid/88180
Third Party AdvisoryVDB Entry
securitytracker.com / id/1035705