Vulnerability Note VU#584606

NTP service vulnerable to internal overflow if date / time offset is greater than 34 years

Overview

NTP (Network TIme Protocol) contains an integer overflow vulnerability that may lead to clients receiving an incorrect date/time offset.

I. Description

NTP (Network Time Protocol) is a method by which client machines can synchronize the local date and time with a reference server. The server will miscalculate the offset reply, if it receives a request from an NTP client containing a date that is more or less than 34 years of the server's date.

This offset is a 64-bit value, with 32 bits representing whole seconds, and 32 bits representing fractions of a second . The 34-year limit is imposed by the use of a 32-bit signed integer.

The NTP server performs a series of calculations, accounting for transmission delay and computing time, resulting in a value which represents the difference between the NTP server time and the requesting machine's time.

The packet sent back to the client is a date/time offset, which is then used to update the client's date/time.

II. Impact

Clients making requests of an NTP server and supplying a date/time that is more than 34 years in the future (or past) from the NTP server date/time will receive an incorrect date/time offset from the server, resulting in an incorrect date/time on the client.

There is no known impact to the NTP server.

III. Solution

NTPd Version 4 resolves this issue.

Systems Affected

Vendor	Status	Date Notified	Date Updated
NTP.org	Vulnerable	5-Mar-2004

References

http://www.eecis.udel.edu/~mills/ntp.html
http://www.eecis.udel.edu/~mills/time.html
http://www.eecis.udel.edu/~mills/y2k.html

Credit

Thanks to David L. Mills of NTP.org for reporting this vulnerability.

This document was written by Robert D Hanson.

Other Information

Date Public:	2004-01-22
Date First Published:	2004-03-05
Date Last Updated:	2004-03-05
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	0.06
Document Revision:	5

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Get Adobe Reader