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Published: 9 December 2019

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

From the Ubuntu Security Team

Miroslav Lichvár discovered a head-based buffer overflow in chrony. A remote attacker could use this vulnerability to cause a denial of service (crash) or execute arbitrary code.



Cvss 3 Severity Score


Score breakdown


Package Release Status
Launchpad, Ubuntu, Debian
artful Not vulnerable
bionic Not vulnerable
cosmic Not vulnerable
lucid Ignored
(reached end-of-life)
precise Does not exist
(precise was needed)
Released (1.29-1ubuntu0.1)
Released (1.31.1)
utopic Ignored
(reached end-of-life)
vivid Ignored
(reached end-of-life)
wily Ignored
(reached end-of-life)
xenial Not vulnerable
yakkety Ignored
(reached end-of-life)
zesty Ignored
(reached end-of-life)

Severity score breakdown

Parameter Value
Base score 6.5
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H