topic Re: NTP vulnerability in Network Security

NTP vulnerability

fadhel Sh — Tue, 05 Sep 2023 12:06:32 GMT

Hi all,

From the vulnerability scan, we got the below issue for NTP for Cisco Switch.

Threat: The NTP service running on the host allows queries of NTP variables.

Impact: A remote user can obtain sensitive information about the host by querying various variables. The information obtained can aid in further attacks against the system.

Solution: Please reconfigure NTP to restrict remote access.

Could somebody please advise how to fix it.

Regards,

Re: NTP vulnerability

M02@rt37 — Tue, 05 Sep 2023 12:47:45 GMT

Hello @fadhel Sh,

Start to limit ntp updates from identified servers

ntp access-group peer XX

XX == ACL standard id with servers identified.

Re: NTP vulnerability

johnd2310 — Tue, 05 Sep 2023 23:57:41 GMT

Hi,

You need to create access lists that restrict queries to your switches but allow your switches to get time from NTP servers. The following is an example:

ip access-list standard 10
permit x.x.x.x
permit y.y.y.y
ip access-list standard 20
deny any
!
ntp access-group peer 10
ntp access-group serve-only 20
ntp access-group query-only 20
ntp server x.x.x.x
ntp server y.y.y.y

Access list 10 specifies the NTP servers that are allowed to provide time to the switch. Access list 20 denies access.

ntp access-group peer 10 specifies that we only get time from servers defined in access list 10.

ntp access-group serve-only 20 specifies that we do not server time to anyone.

ntp access-group query-only 20 specifies that we do no allow queries from anyone.

Thanks