NVD / CVE Program· CNA mitre

CVE-2016-7426: NTP before 4.2.8p9 rate limits responses received from the configured sources when rate limiting for all associations is enabled, which…

HighCVSS 7.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 12.3% (FIRST EPSS); higher than 96.2% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: ntp (Debian:11) 1:4.2.8p9+dfsg-1; ntp (Red Hat:enterprise_linux:6::client) 0:4.2.6p5-10.el6_8.2; ntp-debuginfo (Red Hat:enterprise_linux:6::client) 0:4.2.6p5-10.el6_8.2.

Low priority for now. Upgrade to ntp (Debian:11) 1:4.2.8p9+dfsg-1; ntp (Red Hat:enterprise_linux:6::client) 0:4.2.6p5-10.el6_8.2; ntp-debuginfo (Red Hat:enterprise_linux:6::client) 0:4.2.6p5-10.el6_8.2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published: Jan 13, 2017
Updated: Jun 16, 2026
EPSS: 12.3% · 96th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 4 / 30 · 12.3%

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
ntp	ntp	cpe:2.3:a:ntp:ntp
canonical	ubuntu linux	cpe:2.3:o:canonical:ubuntu_linux
redhat	enterprise linux desktop	cpe:2.3:o:redhat:enterprise_linux_desktop
redhat	enterprise linux server	cpe:2.3:o:redhat:enterprise_linux_server
redhat	enterprise linux server aus	cpe:2.3:o:redhat:enterprise_linux_server_aus
redhat	enterprise linux server eus	cpe:2.3:o:redhat:enterprise_linux_server_eus
redhat	enterprise linux server tus	cpe:2.3:o:redhat:enterprise_linux_server_tus
redhat	enterprise linux workstation	cpe:2.3:o:redhat:enterprise_linux_workstation
hpe	hpux-ntp	cpe:2.3:a:hpe:hpux-ntp

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

canonical ubuntu linux12.04
hpe hpux-ntpb.11.31 and later · before c.4.2.8.2.0
ntp ntp4.2.6 and later · before 4.2.8
ntp ntp4.3.0 and later · before 4.3.94
ntp ntp4.2.5
ntp ntp4.2.8
redhat enterprise linux desktop6.0
redhat enterprise linux desktop7.0

+12 more rows

redhat enterprise linux server6.0
redhat enterprise linux server7.0
redhat enterprise linux server aus7.3
redhat enterprise linux server aus7.4
redhat enterprise linux server aus7.6
redhat enterprise linux server aus7.7
redhat enterprise linux server eus7.3
redhat enterprise linux server eus7.4
redhat enterprise linux server eus7.5
redhat enterprise linux server eus7.6
redhat enterprise linux server eus7.7
redhat enterprise linux server tus7.3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:11	ntp	before 1:4.2.8p9+dfsg-1	1:4.2.8p9+dfsg-1
Red Hat:enterprise_linux:6::client	ntp	before 0:4.2.6p5-10.el6_8.2	0:4.2.6p5-10.el6_8.2
Red Hat:enterprise_linux:6::client	ntp-debuginfo	before 0:4.2.6p5-10.el6_8.2	0:4.2.6p5-10.el6_8.2
Red Hat:enterprise_linux:6::client	ntp-doc	before 0:4.2.6p5-10.el6_8.2	0:4.2.6p5-10.el6_8.2
Red Hat:enterprise_linux:6::client	ntp-perl	before 0:4.2.6p5-10.el6_8.2	0:4.2.6p5-10.el6_8.2
Red Hat:enterprise_linux:6::client	ntpdate	before 0:4.2.6p5-10.el6_8.2	0:4.2.6p5-10.el6_8.2
Red Hat:enterprise_linux:7::client	ntp	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
Red Hat:enterprise_linux:7::client	ntp-debuginfo	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
Red Hat:enterprise_linux:7::client	ntp-doc	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
Red Hat:enterprise_linux:7::client	ntp-perl	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
Red Hat:enterprise_linux:7::client	ntpdate	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
Red Hat:enterprise_linux:7::client	sntp	before 0:4.2.6p5-25.el7_3.1	0:4.2.6p5-25.el7_3.1
SUSE:Linux Enterprise Desktop 12 SP1	ntp	before 4.2.8p9-55.1	4.2.8p9-55.1
SUSE:Linux Enterprise Server 11 SP4	ntp	before 4.2.8p9-57.2	4.2.8p9-57.2
SUSE:Linux Enterprise Server for SAP Applications 12	ntp	before 4.2.8p9-46.18.1	4.2.8p9-46.18.1
SUSE:OpenStack Cloud 5	ntp	before 4.2.8p9-48.9.1	4.2.8p9-48.9.1

Same product

ntp: all records

Other highest-scoring records for the same primary product.

CVE-2015-7871Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.
64This week
CVE-2014-9295Multiple stack-based buffer overflows in ntpd in NTP before 4.2.8 allow remote attackers to execute arbitrary code via a crafted packet…
54Plan
CVE-2013-5211The monlist feature in ntp_request.c in ntpd in NTP before 4.2.7p26 allows remote attackers to cause a denial of service (traffic…
49Plan

Published before and after this one in the same product

← EarlierCVE-2016-1549Jan 6, 2017 · A malicious authenticated peer can create arbitrarily-many ephemeral associations in order to win the clock selection algorithm in ntpd in…
27Monitor
← EarlierCVE-2016-1550Jan 6, 2017 · An exploitable vulnerability exists in the message authentication functionality of libntp in ntp 4.2.8p4 and NTPSec…
22Monitor
Later →CVE-2016-7427Jan 13, 2017 · The broadcast mode replay prevention functionality in ntpd in NTP before 4.2.8p9 allows remote attackers to cause a denial of service…
18Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
debian:ntp	1:4.2.8p9+dfsg-1 · Debian:11	Package registry (OSV)
red hat:ntp	0:4.2.6p5-10.el6_8.2 · Red Hat:enterprise_linux:6::client	Package registry (OSV)
red hat:ntp-debuginfo	0:4.2.6p5-10.el6_8.2 · Red Hat:enterprise_linux:6::client	Package registry (OSV)
red hat:ntp-doc	0:4.2.6p5-10.el6_8.2 · Red Hat:enterprise_linux:6::client	Package registry (OSV)
red hat:ntp-perl	0:4.2.6p5-10.el6_8.2 · Red Hat:enterprise_linux:6::client	Package registry (OSV)
red hat:ntpdate	0:4.2.6p5-10.el6_8.2 · Red Hat:enterprise_linux:6::client	Package registry (OSV)
red hat:sntp	0:4.2.6p5-25.el7_3.1 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
suse:ntp	4.2.8p9-57.2 · SUSE:Linux Enterprise Server 11 SP4	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Bug bounty scope

HPE VDPHackerOne · disclosure only (VDP)

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

For records you follow, these changes also arrive as notifications. →

References

nwtime.org/ntp428p9_release/

Show all references (10 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records