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Vulnerability record · CVE-2016-4955 · published 5 July 2016

CVE-2016-4955: Ntp race condition vulnerability

Ntp · Ntp

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.

5.9 CVSS 3.1 Medium EPSS 8.8% · top 5.0% CWE-362 · Race condition
5.9CVSS 3.1 base score, v2 4.3
8.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
10Affected product versions listed by NVD
62References
17 Jun 2026Last modified by 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.

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

Affected products

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

References

LinkTags
http://bugs.ntp.org/3043 Issue TrackingVendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00020.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-07/msg00026.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00042.html
http://packetstormsecurity.com/files/137321/Slackware-Security-Advisory-ntp-Updates.html
http://packetstormsecurity.com/files/137322/FreeBSD-Security-Advisory-FreeBSD-SA-16-24.ntp.html
http://support.ntp.org/bin/view/Main/NtpBug3043 PatchVendor Advisory
http://support.ntp.org/bin/view/Main/SecurityNotice Release NotesVendor Advisory
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160603-ntpd
http://www.kb.cert.org/vuls/id/321640 Third Party AdvisoryUS Government Resource
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html Third Party Advisory
http://www.securityfocus.com/archive/1/538599/100/0/threaded
http://www.securityfocus.com/archive/1/538600/100/0/threaded
http://www.securityfocus.com/archive/1/archive/1/538599/100/0/threaded
http://www.securityfocus.com/archive/1/archive/1/538600/100/0/threaded
http://www.securityfocus.com/bid/91007 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1036037 Third Party AdvisoryVDB Entry
http://www.ubuntu.com/usn/USN-3096-1
https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K3EYJQHJZ2KTVQ7ICEFHXTL
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORAMN3Q7TVJ54MBYF75XCJO
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WNWGCQLW2VY72NIUYMJOCAK
https://security.FreeBSD.org/advisories/FreeBSD-SA-16:24.ntp.asc Third Party Advisory
https://security.gentoo.org/glsa/201607-15 Third Party Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-159-11
https://www.kb.cert.org/vuls/id/321640
http://bugs.ntp.org/3043 Issue TrackingVendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00020.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-07/msg00026.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00042.html

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Source: NIST National Vulnerability Database (record CVE-2016-4955), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.