Missing limit for accepted NTS-KE connections allows an unauthenticated remote attacker to crash ntpd-rs when an NTS-KE server is configured. Non NTS-KE server configurations, such as the default ntpd-rs configuration, are unaffected.
During startup, an attacker that can man-in-the-middle traffic to and from NTS key exchange servers can trigger a very expensive key validation process due to a vulnerability in webpki.
ntpd-rs does not validate the length of NTS cookies in received NTP packets to the server. An attacker can crash the server by sending a specially crafted NTP packet containing a cookie shorter than what the server expects. The server also crashes when it is not configured to handle NTS packets. ntpd-rs running purely as an ntp client is not affected.