Bug 1397345 (CVE-2016-7426)

Summary:	CVE-2016-7426 ntp: Client rate limiting and server responses
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	apmukher, keyur.three0, mlichvar, sardella, slawomir, yozone
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	ntp-4.2.8p9	Doc Type:	If docs needed, set a value
Doc Text:	It was found that when ntp is configured with rate limiting for all associations the limits are also applied to responses received from its configured sources. A remote attacker who knows the sources can cause a denial of service by preventing ntpd from accepting valid responses from its sources.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-02-06 06:50:32 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1397351, 1411642, 1411643, 1411644, 1411645
Bug Blocks:	1397349

Description Adam Mariš 2016-11-22 10:56:41 UTC

When ntpd is configured with rate limiting for all associations (restrict default limited in ntp.conf), the limits are applied also to responses received from its configured sources. An attacker who knows the sources (e.g., from an IPv4 refid in server response) and knows the system is (mis)configured in this way can periodically send packets with spoofed source address to keep the rate limiting activated and prevent ntpd from accepting valid responses from its sources.

External References:

http://support.ntp.org/bin/view/Main/NtpBug3071

Comment 1 Adam Mariš 2016-11-22 11:09:12 UTC

Created ntp tracking bugs for this issue:

Affects: fedora-all [bug 1397351]

Comment 2 Huzaifa S. Sidhpurwala 2016-12-14 08:14:56 UTC

Mitigation:

If you choose to use restrict default limited ..., be sure to use restrict source ... (without limited) to avoid this attack.

Comment 4 Keyur Pujara 2017-01-16 11:30:27 UTC

Is an RPM released with fix for this. I haven't seen one @ http://mirror.centos.org. 

If not released, what is ETA for same?

Thanks, Keyur

Comment 5 errata-xmlrpc 2017-02-06 06:17:42 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6
  Red Hat Enterprise Linux 7

Via RHSA-2017:0252 https://rhn.redhat.com/errata/RHSA-2017-0252.html