Bug 1384860 (CVE-2016-8858)

Summary:	CVE-2016-8858 openssh: Memory exhaustion due to unregistered KEXINIT handler after receiving message
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	jjelen, sardella, security-response-team, thibaut.pouzet
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-06-08 03:00:07 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:
Bug Blocks:	1384863

Description Adam Mariš 2016-10-14 09:49:41 UTC

A memory exhaustion issue in OpenSSH that can be triggered before user authentication was found. An unauthenticated attacker could consume approx. 400 MB of memory per each connection. The attacker could set up multiple such connections to run out of server’s memory.   

Affected versions: openssh-6.8p1, openssh-6.9p1, openssh-7.0p1, openssh-7.1p1, openssh-7.2p1, openssh-7.3p1. 

Upstream patch:

http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/kex.c?rev=1.127&content-type=text/x-cvsweb-markup

Comment 1 Adam Mariš 2016-10-14 09:49:48 UTC

Acknowledgments:

Name: Shi Lei (Qihoo 360)

Comment 4 Huzaifa S. Sidhpurwala 2016-10-17 05:43:10 UTC

Upstream patch:

https://github.com/openssh/openssh-portable/commit/ec165c392ca54317dbe3064a8c200de6531e89ad

Comment 5 Huzaifa S. Sidhpurwala 2016-10-17 05:47:04 UTC

Analysis:

It seems the only thing the attacker could do here, is self-dos his own connection. Regarding consuming memory on the server, by opening several concurrent connections at the same time, there are various protections available in opensshd_config file, such as "MaxStartups", which can limit the maximum number of sessions per network connections. Based on this we do not consider this to be a security issue.


Statement:

The Red Hat Product Security Team does not consider this issue to be a security flaw, for more information please refer to https://bugzilla.redhat.com/show_bug.cgi?id=1384860#c5

Comment 6 Jakub Jelen 2016-10-17 07:42:14 UTC

*** Bug 1384566 has been marked as a duplicate of this bug. ***

Comment 7 Adam Mariš 2016-10-19 07:53:26 UTC

CVE request:

http://seclists.org/oss-sec/2016/q4/185

Comment 8 Andrej Nemec 2016-10-21 10:52:07 UTC

*** Bug 1387116 has been marked as a duplicate of this bug. ***

Comment 9 Andrej Nemec 2016-10-21 10:52:57 UTC

CVE assignment:

http://seclists.org/oss-sec/2016/q4/191