Public Date:
1434005: CVE-2017-6458 ntp: Potential Overflows in ctl_put() functions
A vulnerability was found in NTP, in the building of response packets with custom fields. If custom fields were configured in ntp.conf with particularly long names, inclusion of these fields in the response packet could cause a buffer overflow, leading to a crash.

Find out more about CVE-2017-6458 from the MITRE CVE dictionary dictionary and NIST NVD.


The security assessment from cure53 clarifies that this issue (identified as NTP-01-0004) is not a vulnerability per se, but a weakness in ntp's internal coding style that may cause a vulnerability if particularly long variable names are defined at compile time. No such variable names are defined in upstream source code, nor in Fedora or Red Hat Enterprise Linux versions of ntp.

CVSS v3 metrics

NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.

CVSS3 Base Score 7.1
CVSS3 Base Metrics CVSS:3.0/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Attack Vector Network
Attack Complexity High
Privileges Required Low
User Interaction Required
Scope Unchanged
Confidentiality High
Integrity Impact High
Availability Impact High

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 7 ntp Not affected
Red Hat Enterprise Linux 6 ntp Not affected
Red Hat Enterprise Linux 5 ntp Not affected


Red Hat would like to thank the NTP project for reporting this issue. Upstream acknowledges Cure53 as the original reporter.


Implement BCP-38.

If you don't want to upgrade, then don't setvar variable names longer than 200-512 bytes in your ntp.conf file.

Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.

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