The Network Time Foundation’s Network Time Protocol Project has patched multiple denial-of-service vulnerabilities with the release of ntp-4.2.8p9. The last update to the open source protocol used to synchronize computer clocks was in June.

“NTP users are strongly urged to take immediate action to ensure that their NTP daemons are not susceptible to being used in DDoS (distributed denial-of-service) attacks,” the project maintainers wrote in the security advisory.