NTP BUG 3389: Denial of Service via Malformed Config

Last update: November 3, 2025 16:09 UTC (9cbb45cb6)

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Summary

Resolved	4.2.8p10	21 Mar 2017
References	Bug 3389	CVE-2017-6464
Affects	All versions of NTP-4, up to but not including ntp-4.2.8p10, and ntp-4.3.0 up to, but not including ntp-4.3.94.	Resolved in 4.2.8p10.
CVSS2 Score	MED 4.6	AV:N/AC:H/Au:M/C:N/I:N/A:C
CVSS3 Score	MED 4.2	CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H

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Description

A vulnerability found in the NTP server makes it possible for an authenticated remote user to crash ntpd via a malformed mode configuration directive.

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Mitigation

• Implement BCP-38.
• Upgrade to 4.2.8p10 or later.
• Properly monitor your ntpd instances, and auto-restart ntpd (without -g) if it stops running.

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Credit

This weakness was discovered by Cure53.

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Timeline

• 2017 Mar 21: Public release
• 2017 Mar 06: Early Access Program Release: Premier and Partner Institutional Members
• 2017 Mar 06: Notification to Institutional Members
• 2017 Feb 09: Mozilla/Cure53 audit received