CVE-2016-1547: An off-path attacker can cause a preemptible client association to be demobilized in NTP 4.2.8p4 and earlier and NTPSec…
Noroxi assessment
Priority: Monitor (action score 23/100)
- 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: 5% (FIRST EPSS); higher than 92.4% 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) 1:4.2.8p7+dfsg-1; ntp (Debian:7) 1:4.2.6.p5+dfsg-2+deb7u7; ntp (Debian:8) 1:4.2.6.p5+dfsg-7+deb8u2.
Low priority for now. Upgrade to ntp (Debian:11) 1:4.2.8p7+dfsg-1; ntp (Debian:7) 1:4.2.6.p5+dfsg-2+deb7u7; ntp (Debian:8) 1:4.2.6.p5+dfsg-7+deb8u2 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
An off-path attacker can cause a preemptible client association to be demobilized in NTP 4.2.8p4 and earlier and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92 by sending a crypto NAK packet to a victim client with a spoofed source address of an existing associated peer. This is true even if authentication is enabled.
- Published
- Jan 6, 2017
- Updated
- Jun 16, 2026
- EPSS
- 5.0% · 92th percentile
- CWE
- CWE-20
Report tools
Action score
23
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 2 / 30 · 5.0%
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 itNoroxi 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 helpAffected 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 |
Versions reported by the vendor
Affected version ranges reported by the assigning authority (certcc). Independent of NVD's CPE analysis and usually ahead of it.
NTP Project NTP
- 4.2.8p3, 4.2.8p4affected
NTPsec Project NTPSec
- a5fb34b9cc89b92a8fef2f459004865c93bb7f92affected
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- ntp ntpup to 4.2.8 inclusive
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 1:4.2.8p7+dfsg-1 | 1:4.2.8p7+dfsg-1 |
| Debian:7 | ntp | before 1:4.2.6.p5+dfsg-2+deb7u7 | 1:4.2.6.p5+dfsg-2+deb7u7 |
| Debian:8 | ntp | before 1:4.2.6.p5+dfsg-7+deb8u2 | 1:4.2.6.p5+dfsg-7+deb8u2 |
| Red Hat:enterprise_linux:6::client | ntp | before 0:4.2.6p5-10.el6.1 | 0:4.2.6p5-10.el6.1 |
| Red Hat:enterprise_linux:6::client | ntp-debuginfo | before 0:4.2.6p5-10.el6.1 | 0:4.2.6p5-10.el6.1 |
| Red Hat:enterprise_linux:6::client | ntp-doc | before 0:4.2.6p5-10.el6.1 | 0:4.2.6p5-10.el6.1 |
| Red Hat:enterprise_linux:6::client | ntp-perl | before 0:4.2.6p5-10.el6.1 | 0:4.2.6p5-10.el6.1 |
| Red Hat:enterprise_linux:6::client | ntpdate | before 0:4.2.6p5-10.el6.1 | 0:4.2.6p5-10.el6.1 |
| Red Hat:enterprise_linux:7::client | ntp | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:enterprise_linux:7::client | ntp-debuginfo | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:enterprise_linux:7::client | ntp-doc | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:enterprise_linux:7::client | ntp-perl | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:enterprise_linux:7::client | ntpdate | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:enterprise_linux:7::client | sntp | before 0:4.2.6p5-22.el7_2.2 | 0:4.2.6p5-22.el7_2.2 |
| Red Hat:rhel_eus:6.7::computenode | ntp | before 0:4.2.6p5-5.el6_7.5 | 0:4.2.6p5-5.el6_7.5 |
| Red Hat:rhel_eus:6.7::computenode | ntp-debuginfo | before 0:4.2.6p5-5.el6_7.5 | 0:4.2.6p5-5.el6_7.5 |
| Red Hat:rhel_eus:6.7::computenode | ntp-doc | before 0:4.2.6p5-5.el6_7.5 | 0:4.2.6p5-5.el6_7.5 |
| Red Hat:rhel_eus:6.7::computenode | ntp-perl | before 0:4.2.6p5-5.el6_7.5 | 0:4.2.6p5-5.el6_7.5 |
| Red Hat:rhel_eus:6.7::computenode | ntpdate | before 0:4.2.6p5-5.el6_7.5 | 0:4.2.6p5-5.el6_7.5 |
| SUSE:Linux Enterprise Desktop 12 | ntp | before 4.2.8p8-46.8.1 | 4.2.8p8-46.8.1 |
| SUSE:Linux Enterprise Server 11 SP4 | ntp | before 4.2.8p7-11.1 | 4.2.8p7-11.1 |
| SUSE:OpenStack Cloud 5 | ntp | before 4.2.8p7-44.1 | 4.2.8p7-44.1 |
Same product
ntp: all recordsOther 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-2016-4957Jul 4, 2016 · ntpd in NTP before 4.2.8p8 allows remote attackers to cause a denial of service (daemon crash) via a crypto-NAK packet.43Plan
- ← EarlierCVE-2015-7848Jan 6, 2017 · An integer overflow can occur in NTP-dev.4.3.70 leading to an out-of-bounds memory copy operation when processing a specially crafted…32Monitor
- Later →CVE-2016-1548Jan 6, 2017 · An attacker can spoof a packet from a legitimate ntpd server with an origin timestamp that matches the peer->dst timestamp recorded for…29Monitor
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 | 1:4.2.8p7+dfsg-1 · Debian:11 | Package registry (OSV) |
| red hat:ntp | 0:4.2.6p5-10.el6.1 · Red Hat:enterprise_linux:6::client | Package registry (OSV) |
| red hat:ntp-debuginfo | 0:4.2.6p5-10.el6.1 · Red Hat:enterprise_linux:6::client | Package registry (OSV) |
| red hat:ntp-doc | 0:4.2.6p5-10.el6.1 · Red Hat:enterprise_linux:6::client | Package registry (OSV) |
| red hat:ntp-perl | 0:4.2.6p5-10.el6.1 · Red Hat:enterprise_linux:6::client | Package registry (OSV) |
| red hat:ntpdate | 0:4.2.6p5-10.el6.1 · Red Hat:enterprise_linux:6::client | Package registry (OSV) |
| red hat:sntp | 0:4.2.6p5-22.el7_2.2 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| suse:ntp | 4.2.8p7-11.1 · 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.
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.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- low · 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
- Low
Weakness class (CWE)
CWE-20 · Improper Input ValidationCVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Server Side Include (SSI) InjectionCAPEC-101likelihood: High · High
- Cross Zone ScriptingCAPEC-104likelihood: Medium · High
- Command Line Execution through SQL InjectionCAPEC-108likelihood: Low · Very High
- Object Relational Mapping InjectionCAPEC-109likelihood: Low · High
- SQL Injection through SOAP Parameter TamperingCAPEC-110likelihood: High · Very High
- Double EncodingCAPEC-120likelihood: Low · Medium
- Subverting Environment Variable ValuesCAPEC-13likelihood: High · Very High
ATT&CK techniques
- Obfuscated Files or InformationT1027
- Masquerading: Invalid Code SignatureT1036.001
- Steal Web Session CookieT1539
- Subvert Trust Controls: Code SigningT1553.002
- Impair Defenses:Impair Command History LoggingT1562.003
- Hijack Execution Flow:Dynamic Linker HijackingT1574.006
- Hijack Execution Flow:Path Interception by PATH Environment VariableT1574.007
Change log (1)
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (14 more)Show less
- www.debian.org/security/2016/dsa-3629
- www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
- www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
- www.securityfocus.com/bid/88276
- www.securitytracker.com/id/1035705
- www.talosintelligence.com/reports/TALOS-2016-0081/
- access.redhat.com/errata/RHSA-2016:1141
- cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf
- cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
- security.FreeBSD.org/advisories/FreeBSD-SA-16:16.ntp.asc
- security.gentoo.org/glsa/201607-15
- security.netapp.com/advisory/ntap-20171004-0002/
- us-cert.cisa.gov/ics/advisories/icsa-21-103-11
- www.arista.com/en/support/advisories-notices/security-advisories/1332-security-advisory-19
Vendor advisories and official records. Exploit/PoC links are deliberately left out.