Bug 1340850 (CVE-2016-4957)

Summary:	CVE-2016-4957 ntp: crypto-NAK DoS (incorrect fix for CVE-2016-1547)
Product:	[Other] Security Response	Reporter:	Martin Prpič <mprpic>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	mlichvar, mprpic, sardella, security-response-team, sparks
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	ntp-4.2.8p7	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-05-30 12:58:58 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:
Bug Blocks:	1302226

Description Martin Prpič 2016-05-30 12:16:57 UTC

It was found that the fix for CVE-2016-1547 introduced a new issue. An attacker could send a crafted packet with crypto-NAK to a server or client that will cause ntpd to crash (segfault on NULL pointer dereference).

The issue was introduced in the original patch for CVE-2016-1547 here:

http://bk1.ntp.org/ntp-stable/?PAGE=patch&REV=56b42514rgZyUCPCWq2Uyhw4BWUpSg

Comment 1 Martin Prpič 2016-05-30 12:17:01 UTC

Acknowledgments:

Name: CERT/CC
Upstream: Nicolas Edet (Cisco)

Comment 2 Martin Prpič 2016-05-30 12:58:58 UTC

Statement:

This issue did not affect the versions of ntp as shipped with any Red Hat Enterprise Linux version as they did not include the same upstream fix for CVE-2016-1547 that introduced the issue. The fix developed by Red Hat for CVE-2016-1547 did not include this issue.

Comment 3 Martin Prpič 2016-06-02 13:41:34 UTC

Upstream bug:

http://support.ntp.org/bin/view/Main/NtpBug3046

External References:

http://support.ntp.org/bin/view/Main/SecurityNotice#June_2016_ntp_4_2_8p8_NTP_Securi