Bug 1384860 - (CVE-2016-8858) CVE-2016-8858 openssh: Memory exhaustion due to unregistered KEXINIT handler after receiving message
CVE-2016-8858 openssh: Memory exhaustion due to unregistered KEXINIT handler ...
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20161017,repor...
: Security
: 1384566 1387116 (view as bug list)
Depends On:
Blocks: 1384863
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Reported: 2016-10-14 05:49 EDT by Adam Mariš
Modified: 2016-10-21 06:52 EDT (History)
5 users (show)

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Description Adam Mariš 2016-10-14 05:49:41 EDT
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 05:49:48 EDT
Acknowledgments:

Name: Shi Lei (Qihoo 360)
Comment 5 Huzaifa S. Sidhpurwala 2016-10-17 01:47:04 EDT
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 03:42:14 EDT
*** Bug 1384566 has been marked as a duplicate of this bug. ***
Comment 7 Adam Mariš 2016-10-19 03:53:26 EDT
CVE request:

http://seclists.org/oss-sec/2016/q4/185
Comment 8 Andrej Nemec 2016-10-21 06:52:07 EDT
*** Bug 1387116 has been marked as a duplicate of this bug. ***
Comment 9 Andrej Nemec 2016-10-21 06:52:57 EDT
CVE assignment:

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

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