CVE-2020-11868 — ntpd in ntp before 4

ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows an off-path attacker to block unauthenticated synchronization via a server mode packet with a spoofed source IP address, because transmissions are rescheduled even when a packet lacks a valid origin timestamp.

01What is this vulnerability?

ntpd in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows an off-path attacker to block unauthenticated synchronization via a server mode packet with a spoofed source IP address, because transmissions are rescheduled even when a packet lacks a valid origin timestamp.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-04-17T03:31:05.000Z
• Last modified: 2025-05-05T17:08:18.997Z

09References

• lists.debian.org — https://lists.debian.org/debian-lts-announce/2020/05/msg00004.html
• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
• security.gentoo.org — https://security.gentoo.org/glsa/202007-12
• www.oracle.com — https://www.oracle.com//security-alerts/cpujul2021.html
• support.ntp.org — http://support.ntp.org/bin/view/Main/NtpBug3592
• bugzilla.redhat.com — https://bugzilla.redhat.com/show_bug.cgi?id=1716665
• security.netapp.com — https://security.netapp.com/advisory/ntap-20200424-0002/