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Vulnerability record · CVE-2018-8956 · published 6 May 2020

CVE-2018-8956: Ntp improper input validation vulnerability

Ntp · Ntp

ntpd in ntp 4.2.8p10, 4.2.8p11, 4.2.8p12 and 4.2.8p13 allow remote attackers to prevent a broadcast client from synchronizing its clock with a broadcast NTP server via soofed mode 3 and mode 5 packets. The attacker must either be a part of the same broadcast network or control a slave in that broadcast network that can capture certain required packets on the attacker's behalf and send them to the attacker.

5.3 CVSS 3.1 Medium EPSS 3.1% · top 12.3% CWE-20 · Improper input validation
5.3CVSS 3.1 base score, v2 5.0
3.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
14References
17 Jun 2026Last modified by NVD

Description

ntpd in ntp 4.2.8p10, 4.2.8p11, 4.2.8p12 and 4.2.8p13 allow remote attackers to prevent a broadcast client from synchronizing its clock with a broadcast NTP server via soofed mode 3 and mode 5 packets. The attacker must either be a part of the same broadcast network or control a slave in that broadcast network that can capture certain required packets on the attacker's behalf and send them to the attacker.

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

Affected products

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

References

LinkTags
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
http://www.ntp.org/ Vendor Advisory
https://arxiv.org/abs/2005.01783 Third Party Advisory
https://nikhiltripathi.in/NTP_attack.pdf Third Party Advisory
https://security.netapp.com/advisory/ntap-20200518-0006/
https://tools.ietf.org/html/rfc5905 Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
http://www.ntp.org/ Vendor Advisory
https://arxiv.org/abs/2005.01783 Third Party Advisory
https://nikhiltripathi.in/NTP_attack.pdf Third Party Advisory
https://security.netapp.com/advisory/ntap-20200518-0006/
https://tools.ietf.org/html/rfc5905 Third Party Advisory

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Related vulnerabilities

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

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Source: NIST National Vulnerability Database (record CVE-2018-8956), CISA KEV, FIRST EPSS (scores of 2026-10-14). This page is refreshed as NVD updates the record.