NTP ntpd Mode 7 Error Response Packet Loop Remote DoS

Medium Nessus Plugin ID 43156


The remote network time service has a denial of service vulnerability.


The version of ntpd running on the remote host has a denial of service vulnerability. It responds to mode 7 error packets with its own mode 7 error packets. A remote attacker could exploit this by sending a mode 7 error response with a spoofed IP header, setting the source and destination IP addresses to the IP address of the target. This would cause ntpd to respond to itself endlessly, consuming excessive amounts of CPU, resulting in a denial of service.


Upgrade to NTP 4.2.4p8 / 4.2.6 or later.

See Also



Plugin Details

Severity: Medium

ID: 43156

File Name: ntpd_mode7_ping_pong_dos.nasl

Version: $Revision: 1.14 $

Type: remote

Family: Misc.

Published: 2009/12/14

Modified: 2016/05/11

Dependencies: 10884

Risk Information

Risk Factor: Medium


Base Score: 6.4

Temporal Score: 5.3

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:P

Temporal Vector: CVSS2#E:F/RL:OF/RC:ND

Vulnerability Information

Required KB Items: NTP/Running

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 2009/12/08

Vulnerability Publication Date: 2009/11/04

Reference Information

CVE: CVE-2009-3563

BID: 37255

OSVDB: 60847

CERT: 568372

Secunia: 37629