NTP BUG 3046: CRYPTO_NAK crash

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

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Summary

Resolved	4.2.8p8	02 June 2016
References	Bug 3046	CVE-2016-4957
Affects	ntp-4.2.8p7, and ntp-4.3.92.	Resolved in 4.2.8p8.
CVSS2 Score	HIGH 7.8	AV:N/AC:L/Au:N/C:N/I:N/A:C
CVSS3 Score	HIGH 7.5	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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Description

The fix for 3007 in ntp-4.2.8p7 contained a bug that could cause ntpd to crash.

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Mitigation

• Implement BCP-38.
• Upgrade to 4.2.8p8 or later.
• If you cannot upgrade from 4.2.8p7, the only other alternatives are to patch your code or filter CRYPTO_NAK packets.
• 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 Nicolas Edet of Cisco.

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Timeline

• 2016 Jun 02: Public release
• 2016 May 24: Early Access Program Release: Premier and Partner Institutional Members
• : Notification to Institutional Members
• : Report received