What’s Vulnerable › Vulnerabilities

CVE-2016-4953

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 17.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2016-07-05 · updated 2026-06-17
• Weakness: CWE-287

Description

ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service (ephemeral-association demobilization) by sending a spoofed crypto-NAK packet with incorrect authentication data at a certain time.

Affected products

• NTP: from 4.2.0 before 4.2.8; from 4.3.0 before 4.3.93; 4.2.8, 4.2.8-p1, 4.2.8-p1-beta1, 4.2.8-p1-beta2, 4.2.8-p1-beta3, 4.2.8-p1-beta4 (+15) — fixed in 4.2.8, 4.3.93
• openSUSE Leap: 42.1
• Opensuse: 13.2
• Oracle Corporation Solaris Operating System: 10, 11.3
• Siemens Simatic Net Cp 443-1 Opc Ua Firmware: all versions
• Siemens Tim 4R-Ie Dnp3 Firmware: all versions
• Siemens Tim 4R-Ie Firmware: all versions
• SUSE Linux Enterprise Server 15 SP1: 12-sp1
• SUSE Linux Enterprise Server: 11-sp2, 11-sp3, 11-sp4, 12-sp1
• SUSE Manager: 2.1
• SUSE Manager Proxy: 2.1
• SUSE Openstack Cloud: 5

How to fix

Upgrade to a fixed version: NTP 4.2.8, 4.3.93. Check the vendor advisory for mitigations.

References

• http://bugs.ntp.org/3045
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00020.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.html
• 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/NtpBug3045

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