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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-11868
• https://bugzilla.redhat.com/show_bug.cgi?id=1716665
• https://lists.debian.org/debian-lts-announce/2020/05/msg00004.html
• https://security.gentoo.org/glsa/202007-12
• https://security.netapp.com/advisory/ntap-20200424-0002/
• https://www.oracle.com//security-alerts/cpujul2021.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00005.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00044.html
• http://support.ntp.org/bin/view/Main/NtpBug3592