NTP BUG 2917: Infinite loop if extended logging enabled and the logfile and keyfile are the same

Last update: April 22, 2024 18:49 UTC (7e7bd5857)


Resolved 4.2.8p4 21 Oct 2015
References Bug 2917 CVE-2015-7850
Affects All ntp-4 releases up to, but not including 4.2.8p4,
and 4.3.0 up to, but not including 4.3.77.
Resolved in 4.2.8p4
CVSS2 Score 4.6, worst case AV:N/AC:H/Au:M/C:N/I:N/A:C


If ntpd is configured to allow remote configuration, and if the (possibly spoofed) source IP address is allowed to send remote configuration requests, and if the attacker knows the remote configuration password or if ntpd was configured to disable authentication, then an attacker can send a set of packets to ntpd that will cause it to crash and/or create a potentially huge log file. Specifically, the attacker could enable extended logging, point the key file at the log file, and cause what amounts to an infinite loop.



This weakness was discovered by Yves Younan of Cisco Talos.