ntp: Client rate limiting and server responses
Published Jan 13, 2017
7.5
HIGHCVSS 3.1
EPSS 12.47%
Description
NTP before 4.2.8p9 rate limits responses received from the configured sources when rate limiting for all associations is enabled, which allows remote attackers to cause a denial of service (prevent responses from the sources) by sending responses with a spoofed source address.
Affected products
No data.
Configuration 1
- ≥ 4.2.6 · < 4.2.8
- ≥ 4.3.0 · < 4.3.94
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 4.2.5
- 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
- 4.2.8
Configuration 2
- 12.04
Configuration 3
- 6.0
- 7.0
- 6.0
- 7.0
- 7.3
- 7.4
- 7.6
- 7.7
- 7.3
- 7.4
- 7.5
- 7.6
- 7.7
- 7.3
- 7.6
- 7.7
- 6.0
- 7.0
Configuration 4
- ≥ b.11.31 · < c.4.2.8.2.0
No data.
Red Hat Enterprise Linux 6
ntp-0:4.2.6p5-10.el6_8.2
Fixed · RHSA-2017:0252
Red Hat Enterprise Linux 7
ntp-0:4.2.6p5-25.el7_3.1
Fixed · RHSA-2017:0252
Red Hat Enterprise Linux 5
ntp
Will not fix
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 6 | ntp-0:4.2.6p5-10.el6_8.2 | Fixed | RHSA-2017:0252 |
| Red Hat Enterprise Linux 7 | ntp-0:4.2.6p5-25.el7_3.1 | Fixed | RHSA-2017:0252 |
| Red Hat Enterprise Linux 5 | ntp | Will not fix | n/a |
No package ranges for this CVE.
Remediation
Red Hat mitigation
If you choose to use restrict default limited ..., be sure to use restrict source ... (without limited) to avoid this attack.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
AV:N/AC:M/Au:N/C:N/I:N/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
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 (25 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 12.47% (0.12466) | 96.10th | v5 (v2026.06.15) |
| Jun 15, 2026 | 12.37% (0.12367) | 95.67th | v5 (v2026.06.15) |
| Jan 18, 2026 | 11.68% (0.11683) | 93.46th | v4 (v2025.03.14) |
| Dec 28, 2025 | 41.88% (0.41876) | 97.29th | v4 (v2025.03.14) |
| Dec 27, 2025 | 47.20% (0.47200) | 97.59th | v4 (v2025.03.14) |
| Dec 19, 2025 | 41.88% (0.41876) | 97.28th | v4 (v2025.03.14) |
| Dec 15, 2025 | 48.44% (0.48438) | 97.62th | v4 (v2025.03.14) |
| Dec 13, 2025 | 50.95% (0.50955) | 97.74th | v4 (v2025.03.14) |
| Dec 9, 2025 | 47.20% (0.47200) | 97.55th | v4 (v2025.03.14) |
| Aug 10, 2025 | 38.91% (0.38912) | 97.13th | v4 (v2025.03.14) |
| Jun 19, 2025 | 47.20% (0.47200) | 97.53th | v4 (v2025.03.14) |
| Mar 30, 2025 | 33.24% (0.33243) | 96.54th | v4 (v2025.03.14) |
| Mar 29, 2025 | 22.06% (0.22060) | 93.15th | v4 (v2025.03.14) |
| Mar 19, 2025 | 38.91% (0.38912) | 96.83th | v4 (v2025.03.14) |
| Mar 17, 2025 | 35.06% (0.35062) | 96.67th | v4 (v2025.03.14) |
| Dec 17, 2024 | 3.77% (0.03766) | 91.71th | v3 (v2023.03.01) |
| Apr 15, 2024 | 5.77% (0.05769) | 93.25th | v3 (v2023.03.01) |
| Jan 26, 2024 | 5.14% (0.05141) | 92.21th | v3 (v2023.03.01) |
| Dec 17, 2023 | 4.41% (0.04413) | 91.52th | v3 (v2023.03.01) |
| Nov 4, 2023 | 4.28% (0.04278) | 91.33th | v3 (v2023.03.01) |
| Apr 19, 2023 | 3.84% (0.03842) | 90.53th | v3 (v2023.03.01) |
| Mar 7, 2023 | 3.79% (0.03791) | 90.44th | v3 (v2023.03.01) |
| Mar 6, 2023 | 2.17% (0.02172) | 80.77th | v2 (v2022.01.01) |
| Apr 1, 2022 | 2.17% (0.02172) | 78.91th | v2 (v2022.01.01) |
| Feb 4, 2022 | 2.17% (0.02172) | 57.73th | v2 (v2022.01.01) |
References (15)
- http://nwtime.org/ntp428p9_release/ x_refsource_CONFIRMThird Party Advisory
- http://rhn.redhat.com/errata/RHSA-2017-0252.html vendor-advisoryx_refsource_REDHATThird Party Advisory
- http://support.ntp.org/bin/view/Main/NtpBug3071 x_refsource_CONFIRMIssue TrackingMitigationVendor Advisory
- http://support.ntp.org/bin/view/Main/SecurityNotice#Recent_Vulnerabilities x_refsource_CONFIRMRelease NotesVendor Advisory
- http://www.securityfocus.com/bid/94451 vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
- http://www.securitytracker.com/id/1037354 vdb-entryx_refsource_SECTRACKThird Party AdvisoryVDB Entry
- https://access.redhat.com/security/cve/CVE-2016-7426 Vendor Advisory
- https://bto.bluecoat.com/security-advisory/sa139 x_refsource_CONFIRMThird Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1397345 Issue Tracking
- https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03706en_us x_refsource_CONFIRMThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2016-7426
- https://security.FreeBSD.org/advisories/FreeBSD-SA-16:39.ntp.asc vendor-advisoryx_refsource_FREEBSDThird Party Advisory
- https://usn.ubuntu.com/3707-2/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2016-7426
- https://www.kb.cert.org/vuls/id/633847 third-party-advisoryx_refsource_CERT-VNThird Party AdvisoryUS Government Resource
Change history (0)
No recorded changes yet.