Exit Condition in NTPsec ntpd 1.1.4 to 1.2.5 via NTS Request

Executive Summary

This vulnerability involves a reachable exit condition in NTPsec ntpd versions 1.1.4 through 1.2.5. A remote attacker can terminate the NTP daemon by sending an NTS request with too many NTS Cookie Placeholder extension fields. The issue stems from improper validation of cookie lengths and lack of limits on placeholder counts, allowing excessive placeholders before the real cookie.

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Detection Guidance

Monitor NTPsec ntpd daemon logs for unusual termination events or excessive NTS Cookie Placeholder extension fields. Check for crashes or restarts in ntpd processes. Use network monitoring tools to inspect NTS request packets for abnormal numbers of Cookie Placeholder extensions.

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Impact Analysis

This vulnerability can cause denial of service by crashing the NTP server, disrupting time synchronization services. Attackers may exploit it to make the server unresponsive, affecting systems relying on accurate timekeeping for security, logging, or authentication.

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Mitigation Strategies

Update NTPsec ntpd to a version that includes the fix for NTS Cookie Placeholder handling. If immediate update is not possible, restrict network access to ntpd or disable NTS functionality until patched. Monitor for signs of exploitation attempts targeting NTS requests.

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