DoS Vulnerability in ntpd-rs

# Summary A denial of service vulnerability was discovered in ntpd-rs where an attacker can induce a message storm between two NTP servers running ntpd-rs. # Details Since ntpd-rs version 1.2.0, when configured as a server, incorrectly responded to all NTP messages sent to the server's port with a time reply, including to responses from other servers. As a consequence, a message with a spoofed IP address of another server could cause two servers running ntpd-rs to continually respond to each other, consuming significant amounts of resources. # Impact Any time server running ntpd-rs with version between 1.2.0 and 1.6.1 inclusive which allows non-NTS traffic is affected. Client-only configurations are not affected. Affected users are recommended to upgrade to version 1.6.2 as soon as possible. # Workarounds Should upgrading not be possible, the impact of the issue can be mitigated by: - Whitelisting access to only IP addresses of clients using the server, using the ignore filter method. - Blocking incoming non-request traffic on the NTP server port using a firewall. - Disabling public access to the vulnerable NTP server - Disabling the server functionality by removing any [server] sections from the configuration. # Acknowledgements The ntpd-rs authors thank Eric Sesterhenn from X41 D-Sec GmbH for finding and reporting this issue.

Source published

29 Aug 2025 20:07:27 UTC

Source modified

29 Aug 2025 21:58:17 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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