What’s Vulnerable › Vulnerabilities

CVE-2016-4955

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 8.8% 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-362

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.

Affected products

• Novell Suse Manager: 2.1
• 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
• SUSE Linux Enterprise Server 15 SP1: 12-sp1
• SUSE Linux Enterprise Server: 11-sp2, 11-sp3, 11-sp4, 12-sp1
• 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/3043
• 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/NtpBug3043

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