CVE-2016-4955
MEDIUMCVSS 5.9/10EPSS 8.80%
Last modified
CVE-2016-4955 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. 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.. EPSS estimates a 8.80% chance of exploitation in the next 30 days.
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.
Metrics
Weakness Enumeration
Affected Software
| Vendor | Product | Versions | Update |
|---|---|---|---|
| Ntp | Ntp | >= 4.2.0, < 4.2.8 | — |
| Ntp | Ntp | >= 4.3.0, < 4.3.93 | — |
| Ntp | Ntp | 4.2.8 | — |
| Oracle | Solaris | 10 | — |
| Oracle | Solaris | 11.3 | — |
| Suse | Manager Proxy | 2.1 | — |
| Suse | Openstack Cloud | 5 | — |
| Novell | Suse Manager | 2.1 | — |
| Opensuse | Leap | 42.1 | — |
| Opensuse | Opensuse | 13.2 | — |
| Suse | Linux Enterprise Desktop | 12 | Sp1 |
| Suse | Linux Enterprise Server | 11 | Sp2 |
| Suse | Linux Enterprise Server | 12 | Sp1 |
| Siemens | Simatic Net Cp 443-1 Opc Ua Firmware | All versions | — |
References
- https://bugs.ntp.org/3043Issue Tracking, Vendor Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.htmlMailing List, Third Party Advisory
- https://support.ntp.org/bin/view/Main/NtpBug3043Patch, Vendor Advisory
- https://support.ntp.org/bin/view/Main/SecurityNoticeRelease Notes, Vendor Advisory
- https://www.kb.cert.org/vuls/id/321640Third Party Advisory, US Government Resource
- https://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.htmlThird Party Advisory
- https://www.securityfocus.com/bid/91007Third Party Advisory, VDB Entry
- https://www.securitytracker.com/id/1036037Third Party Advisory, VDB Entry
- https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdfThird Party Advisory
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:24.ntp.ascThird Party Advisory
- https://security.gentoo.org/glsa/201607-15Third Party Advisory
- https://bugs.ntp.org/3043Issue Tracking, Vendor Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.htmlMailing List, Third Party Advisory
- https://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.htmlMailing List, Third Party Advisory
- https://support.ntp.org/bin/view/Main/NtpBug3043Patch, Vendor Advisory
- https://support.ntp.org/bin/view/Main/SecurityNoticeRelease Notes, Vendor Advisory
- https://www.kb.cert.org/vuls/id/321640Third Party Advisory, US Government Resource
- https://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.htmlThird Party Advisory
- https://www.securityfocus.com/bid/91007Third Party Advisory, VDB Entry
- https://www.securitytracker.com/id/1036037Third Party Advisory, VDB Entry
- https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdfThird Party Advisory
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:24.ntp.ascThird Party Advisory
- https://security.gentoo.org/glsa/201607-15Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2016-4955?
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.
How severe is CVE-2016-4955?
CVE-2016-4955 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 8.80% probability of exploitation in the next 30 days.
How do I fix CVE-2016-4955?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
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