Improper input validation in NTP
Priority LOW 32CWE-20Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Partial Red Hat: 20 fixed, 1 without a fix
Attack profile from CVSS 3.0 · NVD. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
EPSS 0.05068 92nd percentileScored 2026-11-07
Fix Partial Red Hat: 2 advisoriesRed Hat: 20 fixed, 1 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| NTP Project | NTP | 4.2.8p3; 4.2.8p4 | — | No fix listed | CNA |
| NTP Project | NTPSec | a5fb34b9cc89b92a8fef2f459004865c93bb7f92 | — | No fix listed | CNA |
- NTP VendorNTP Project Affected 4.2.8p3; 4.2.8p4 Fixed in — No fix listed CNA
- NTPSec VendorNTP Project Affected a5fb34b9cc89b92a8fef2f459004865c93bb7f92 Fixed in — No fix listed CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:ntp:ntp:*:p4:*:*:*:*:*:* | up to 4.2.8 | Vulnerable | NTP Project |
- cpe:2.3:a:ntp:ntp:*:p4:*:*:*:*:*:* Versions up to 4.2.8 Vulnerable ·NTP Project
Remediation
Red Hat 2 advisories
- RHSA-2016:1552 Released 2016-08-03 · Red Hat rating Moderatentp security update
- Red Hat Enterprise Linux HPC Node EUS (v. 6.7) ntp-4.2.6p5-5.el6_7.5, ntpdate-4.2.6p5-5.el6_7.5
- Red Hat Enterprise Linux HPC Node Optional EUS (v. 6.7) ntp-doc-4.2.6p5-5.el6_7.5, ntp-perl-4.2.6p5-5.el6_7.5
- Red Hat Enterprise Linux Server EUS (v. 6.7) ntp-4.2.6p5-5.el6_7.5, ntpdate-4.2.6p5-5.el6_7.5
- Red Hat Enterprise Linux Server Optional EUS (v. 6.7) ntp-doc-4.2.6p5-5.el6_7.5, ntp-perl-4.2.6p5-5.el6_7.5
- RHSA-2016:1141 Released 2016-05-31 · Red Hat rating Moderatentp security update
- Red Hat Enterprise Linux Client (v. 7) ntp-4.2.6p5-22.el7_2.2, ntpdate-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux Client Optional (v. 7) ntp-doc-4.2.6p5-22.el7_2.2, ntp-perl-4.2.6p5-22.el7_2.2, sntp-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux ComputeNode (v. 7) ntp-4.2.6p5-22.el7_2.2, ntpdate-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux ComputeNode Optional (v. 7) ntp-doc-4.2.6p5-22.el7_2.2, ntp-perl-4.2.6p5-22.el7_2.2, sntp-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux Desktop (v. 6) ntp-4.2.6p5-10.el6.1, ntpdate-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Desktop Optional (v. 6) ntp-doc-4.2.6p5-10.el6.1, ntp-perl-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux HPC Node (v. 6) ntp-4.2.6p5-10.el6.1, ntpdate-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux HPC Node Optional (v. 6) ntp-doc-4.2.6p5-10.el6.1, ntp-perl-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Server (v. 6) ntp-4.2.6p5-10.el6.1, ntpdate-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Server (v. 7) ntp-4.2.6p5-22.el7_2.2, ntpdate-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux Server Optional (v. 6) ntp-doc-4.2.6p5-10.el6.1, ntp-perl-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Server Optional (v. 7) ntp-doc-4.2.6p5-22.el7_2.2, ntp-perl-4.2.6p5-22.el7_2.2, sntp-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux Workstation (v. 6) ntp-4.2.6p5-10.el6.1, ntpdate-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Workstation (v. 7) ntp-4.2.6p5-22.el7_2.2, ntpdate-4.2.6p5-22.el7_2.2
- Red Hat Enterprise Linux Workstation Optional (v. 6) ntp-doc-4.2.6p5-10.el6.1, ntp-perl-4.2.6p5-10.el6.1
- Red Hat Enterprise Linux Workstation Optional (v. 7) ntp-doc-4.2.6p5-22.el7_2.2, ntp-perl-4.2.6p5-22.el7_2.2, sntp-4.2.6p5-22.el7_2.2
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 5 | Affected | No fix planned: Will not fix |
| Red Hat Enterprise Linux Client (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Client Optional (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux ComputeNode (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux ComputeNode Optional (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Desktop (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Desktop Optional (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux HPC Node (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux HPC Node EUS (v. 6.7) | Fixed | RHSA-2016:1552 |
| Red Hat Enterprise Linux HPC Node Optional (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux HPC Node Optional EUS (v. 6.7) | Fixed | RHSA-2016:1552 |
| Red Hat Enterprise Linux Server (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Server (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Server EUS (v. 6.7) | Fixed | RHSA-2016:1552 |
| Red Hat Enterprise Linux Server Optional (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Server Optional (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Server Optional EUS (v. 6.7) | Fixed | RHSA-2016:1552 |
| Red Hat Enterprise Linux Workstation (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Workstation (v. 7) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Workstation Optional (v. 6) | Fixed | RHSA-2016:1141 |
| Red Hat Enterprise Linux Workstation Optional (v. 7) | Fixed | RHSA-2016:1141 |
Timeline
- 2026-10-02 Threatist record created from CVE-2016-1547
- 2026-10-03 Alias added: GHSA-hqqw-v32x-33cf
References
Advisory 6
Other 7
- http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
- http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
- https://security.netapp.com/advisory/ntap-20171004-0002/
- https://cert-portal.siemens.com/productcert/pdf/ssa-497656.pdf
- https://us-cert.cisa.gov/ics/advisories/icsa-21-103-11
- https://cert-portal.siemens.com/productcert/pdf/ssa-211752.pdf
- https://www.arista.com/en/support/advisories-notices/security-advisories/1332-security-advisory-19
More NTP Project Ntp vulnerabilities
- TI-2015-06541 Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows… CVSS 3.1CRITICAL 9.8
- TI-2014-07543 Multiple stack-based buffer overflows in ntpd in NTP before 4.2.8 allow remote attackers… CVSS 2.0HIGH 7.5
- TI-2013-04524 The monlist feature in ntp_request.c in ntpd in NTP before 4.2.7p26 allows remote… CVSS 2.0MEDIUM 5.0
- TI-2016-06333 The read_mru_list function in NTP before 4.2.8p9 allows remote attackers to cause a… CVSS 3.1HIGH 7.5
- TI-2018-08842 Stack-based buffer overflow in ntpq and ntpdc of NTP version 4.2.8p11 allows an attacker… CVSS 3.0CRITICAL 9.8
- TI-2016-04280 ntpd in NTP before 4.2.8p8 allows remote attackers to cause a denial of service (daemon… CVSS 3.1HIGH 7.5
Sources
- CVE-2016-1547 · CVE Program
- CVE-2016-1547 · NVD
- FIRST EPSS
- GHSA-hqqw-v32x-33cf · GitHub Advisory Database · CC BY 4.0
- CVE-2016-1547 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences