MEDIUM
ntp: autokey association reset
Published Jul 5, 2016
5.9
MEDIUMCVSS 3.1
EPSS 8.77%
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
No data.
Configuration 1
OR
- ≥ 4.2.0 · < 4.2.8
- ≥ 4.3.0 · < 4.3.93
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
- 4.2.8
Configuration 3
OR
- 2.1
- 5
- 2.1
- 42.1
- 13.2
- 12
- 11
- 11
- 11
- 12
Configuration 4
AND
Running on/with
- n/a
No data.
Red Hat Enterprise Linux 5
ntp
Will not fix
Red Hat Enterprise Linux 6
ntp
Will not fix
Red Hat Enterprise Linux 7
ntp
Will not fix
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 5 | ntp | Will not fix | n/a |
| Red Hat Enterprise Linux 6 | ntp | Will not fix | n/a |
| Red Hat Enterprise Linux 7 | ntp | Will not fix | n/a |
No package ranges for this CVE.
Remediation
Red Hat mitigation
Disable autokey authentication. Instead, configure ntp to use symmetric key authentication, or no authentication at all (if not required). To configure ntp with symmetric key authentication, follow the steps at https://access.redhat.com/solutions/393663
Metrics
No CVSS v4.0 score for this CVE.
5.9 MEDIUM NVD
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector Network
Attack Complexity High
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality Impact None
Integrity Impact None
Availability Impact High
No CVSS v3.0 score for this CVE.
4.3 MEDIUM NVD
AV:N/AC:M/Au:N/C:N/I:N/A:P
Access Vector Network
Access Complexity Medium
Authentication None
Confidentiality Impact None
Integrity Impact None
Availability Impact Partial
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
8.77% 0.08771
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
EPSS probability 0.08771
Score over time
2022–2026- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (18 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 8.77% (0.08771) | 95.02th | v5 (v2026.06.15) |
| Jun 15, 2026 | 8.80% (0.08803) | 94.49th | v5 (v2026.06.15) |
| Feb 18, 2026 | 1.95% (0.01954) | 83.15th | v4 (v2025.03.14) |
| Jan 14, 2026 | 8.08% (0.08080) | 91.88th | v4 (v2025.03.14) |
| Jun 19, 2025 | 4.67% (0.04669) | 88.83th | v4 (v2025.03.14) |
| Mar 17, 2025 | 7.92% (0.07919) | 91.42th | v4 (v2025.03.14) |
| Dec 17, 2024 | 8.42% (0.08418) | 94.40th | v3 (v2023.03.01) |
| Dec 12, 2024 | 2.25% (0.02253) | 89.97th | v3 (v2023.03.01) |
| Apr 27, 2024 | 2.11% (0.02114) | 89.02th | v3 (v2023.03.01) |
| Feb 21, 2024 | 1.83% (0.01831) | 87.85th | v3 (v2023.03.01) |
| Oct 5, 2023 | 1.60% (0.01599) | 85.89th | v3 (v2023.03.01) |
| Jul 17, 2023 | 1.32% (0.01319) | 84.14th | v3 (v2023.03.01) |
| Jun 7, 2023 | 1.12% (0.01123) | 82.59th | v3 (v2023.03.01) |
| Apr 25, 2023 | 1.09% (0.01087) | 82.21th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.73% (0.00734) | 77.81th | v3 (v2023.03.01) |
| Mar 6, 2023 | 4.36% (0.04358) | 88.02th | v2 (v2022.01.01) |
| Apr 1, 2022 | 4.36% (0.04358) | 86.83th | v2 (v2022.01.01) |
| Feb 4, 2022 | 4.36% (0.04358) | 70.59th | v2 (v2022.01.01) |
Weaknesses (1)
References (36)
- http://bugs.ntp.org/3043 x_refsource_CONFIRMIssue TrackingVendor Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00018.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00020.html vendor-advisoryx_refsource_SUSE
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00023.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00024.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00028.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00040.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2016-07/msg00026.html vendor-advisoryx_refsource_SUSE
- http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00042.html vendor-advisoryx_refsource_SUSE
- http://packetstormsecurity.com/files/137321/Slackware-Security-Advisory-ntp-Updates.html x_refsource_MISC
- http://packetstormsecurity.com/files/137322/FreeBSD-Security-Advisory-FreeBSD-SA-16-24.ntp.html x_refsource_MISC
- http://support.ntp.org/bin/view/Main/NtpBug3043 x_refsource_CONFIRMPatchVendor Advisory
- http://support.ntp.org/bin/view/Main/SecurityNotice x_refsource_CONFIRMRelease NotesVendor Advisory
- http://support.ntp.org/bin/view/Main/SecurityNotice#June_2016_ntp_4_2_8p8_NTP_Securi
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160603-ntpd vendor-advisoryx_refsource_CISCO
- http://www.kb.cert.org/vuls/id/321640 third-party-advisoryx_refsource_CERT-VNThird Party AdvisoryUS Government Resource
- http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html x_refsource_CONFIRMThird Party Advisory
- http://www.securityfocus.com/archive/1/538599/100/0/threaded mailing-listx_refsource_BUGTRAQ
- http://www.securityfocus.com/archive/1/538600/100/0/threaded mailing-listx_refsource_BUGTRAQ
- http://www.securityfocus.com/archive/1/archive/1/538599/100/0/threaded mailing-listx_refsource_BUGTRAQ
- http://www.securityfocus.com/archive/1/archive/1/538600/100/0/threaded mailing-listx_refsource_BUGTRAQ
- http://www.securityfocus.com/bid/91007 vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
- http://www.securitytracker.com/id/1036037 vdb-entryx_refsource_SECTRACKThird Party AdvisoryVDB Entry
- http://www.ubuntu.com/usn/USN-3096-1 vendor-advisoryx_refsource_UBUNTU
- https://access.redhat.com/security/cve/CVE-2016-4955 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1340858 Issue Tracking
- https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf x_refsource_CONFIRMThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K3EYJQHJZ2KTVQ7ICEFHXTLZ36MRASWX/ vendor-advisoryx_refsource_FEDORA
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORAMN3Q7TVJ54MBYF75XCJOE3DP7LYHT/ vendor-advisoryx_refsource_FEDORA
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WNWGCQLW2VY72NIUYMJOCAKJKTXHDUK2/ vendor-advisoryx_refsource_FEDORA
- https://nvd.nist.gov/vuln/detail/CVE-2016-4955
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:24.ntp.asc vendor-advisoryx_refsource_FREEBSDThird Party Advisory
- https://security.gentoo.org/glsa/201607-15 vendor-advisoryx_refsource_GENTOOThird Party Advisory
- https://us-cert.cisa.gov/ics/advisories/icsa-21-159-11 x_refsource_MISC
- https://www.cve.org/CVERecord?id=CVE-2016-4955
- https://www.kb.cert.org/vuls/id/321640 third-party-advisoryx_refsource_CERT-VN
Change history (0)
No recorded changes yet.
Sources
CVE.org / MITRE
Status PUBLISHED
Assigner mitre
Published Jul 5, 2016
Updated Aug 6, 2024
Reserved May 23, 2016
Link CVE-2016-4955
CISA Vulnrichment
Updated n/a