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NVD / CVE Program· CNA mitre

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…

MediumCVSS 5.9 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 26/100)

  • 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: 8.7% (FIRST EPSS); higher than 95.2% 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. Special conditions such as timing or configuration are required.
  • Fixed version: ntp (Debian:11) 1:4.2.8p8+dfsg-1; ntp (SUSE:Linux Enterprise Desktop 12) 4.2.8p8-46.8.1; ntp (SUSE:Linux Enterprise Desktop 12 SP1) 4.2.8p8-14.1.

Low priority for now. Upgrade to ntp (Debian:11) 1:4.2.8p8+dfsg-1; ntp (SUSE:Linux Enterprise Desktop 12) 4.2.8p8-46.8.1; ntp (SUSE:Linux Enterprise Desktop 12 SP1) 4.2.8p8-14.1 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

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.

Published
Jul 4, 2016
Updated
Jun 16, 2026
EPSS
8.7% · 95th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
3 / 30 · 8.7%

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.

Follow CVE-2016-4955

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

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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.

VendorProduct
ntpntp
oraclesolaris
susemanager proxy
suseopenstack cloud
novellsuse manager
opensuseleap
opensuseopensuse
suselinux enterprise desktop
suselinux enterprise server
siemenssimatic net cp 443-1 opc ua firmware
siemenssimatic net cp 443-1 opc ua

Affected versions

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

  • novell suse manager2.1
  • ntp ntp4.3.0 and later · before 4.3.93
  • ntp ntp4.2.0 and later · before 4.2.8
  • ntp ntp4.2.8
  • opensuse leap42.1
  • opensuse opensuse13.2
  • oracle solaris10
  • oracle solaris11.3
+6 more rows
  • siemens simatic net cp 443-1 opc ua firmwareall versions
  • suse linux enterprise desktop12
  • suse linux enterprise server11
  • suse linux enterprise server12
  • suse manager proxy2.1
  • suse openstack cloud5

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:11ntpbefore 1:4.2.8p8+dfsg-11:4.2.8p8+dfsg-1
SUSE:Linux Enterprise Desktop 12ntpbefore 4.2.8p8-46.8.14.2.8p8-46.8.1
SUSE:Linux Enterprise Desktop 12 SP1ntpbefore 4.2.8p8-14.14.2.8p8-14.1
SUSE:OpenStack Cloud 5ntpbefore 4.2.8p8-47.34.2.8p8-47.3

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-2016-4953Jul 4, 2016 · ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service (ephemeral-association demobilization) by sending a…
    35Monitor
  • ← EarlierCVE-2016-4954Jul 4, 2016 · The process_packet function in ntp_proto.c in ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service…
    34Monitor
  • Later →CVE-2016-4956Jul 4, 2016 · ntpd in NTP 4.x before 4.2.8p8 allows remote attackers to cause a denial of service (interleaved-mode transition and time change) via a…
    26Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
debian:ntp1:4.2.8p8+dfsg-1 · Debian:11Package registry (OSV)
suse:ntp4.2.8p8-14.1 · SUSE:Linux Enterprise Desktop 12 SP1Package 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.

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

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.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

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

nvd-primary

Attack context

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

ATT&CK techniques

—

References

Show all references (19 more)

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

All records