Is CVE-2016-4955 in the CISA KEV catalog?

No. CVE-2016-4955 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2016-4955?

CVE-2016-4955 has a CVSS v3 base score of 5.9 (MEDIUM).

What is the EPSS score for CVE-2016-4955?

CVE-2016-4955 has an EPSS score of 8.80% (95th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2016-4955?

Upgrade ntp on debian 11 to 1:4.2.8p8+dfsg-1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2016-4955

MEDIUMEPSS 95th pctl

5.9

CVSS v3

NVD

Description

ntpd in NTP 4.x before 4.2.8p8, when autokey is enabled, allows remote attackers to cause a denial of service (peer-variable clearing and association outage) by sending (1) a spoofed crypto-NAK packet or (2) a packet with an incorrect MAC value at a certain time.

CWE-362Race Condition

How to fix

Remediation Available

ntpDebian

Fixed in:1:4.2.8p8+dfsg-1CVE-2016-4955

ntpUbuntu

Fixed in:1:4.2.6.p5+dfsg-3ubuntu2.14.04.10USN-3096-1

Fixed in:1:4.2.8p4+dfsg-3ubuntu5.3USN-3096-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

8.80%probability of exploitation in 30 days

95thpercentile

High risk: more likely to be exploited than 95% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-06.