Bug 809938 (CVE-2011-5000)

Summary:	CVE-2011-5000 openssh: post-authentication resource exhaustion bug via GSSAPI
Product:	[Other] Security Response	Reporter:	Vincent Danen <vdanen>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	jrusnack, mattias.ellert, mgrepl, mvadkert, plautrba, tmraz
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	openssh 5.9	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-03-05 12:42:14 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:	809939, 813196
Bug Blocks:

Description Vincent Danen 2012-04-04 17:19:40 UTC

Common Vulnerabilities and Exposures assigned an identifier CVE-2011-5000 to
the following vulnerability:

Name: CVE-2011-5000
URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-5000
Assigned: 20111224
Reference: FULLDISC:20110801 Useless OpenSSH resources exhausion bug via GSSAPI
Reference: http://seclists.org/fulldisclosure/2011/Aug/2
Reference: http://site.pi3.com.pl/adv/ssh_1.txt

The ssh_gssapi_parse_ename function in gss-serv.c in OpenSSH 5.8 and
earlier, when gssapi-with-mic authentication is enabled, allows remote
authenticated users to cause a denial of service (memory consumption)
via a large value in a certain length field.  NOTE: there may be
limited scenarios in which this issue is relevant.


The upstream fix for this is here:

http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/gss-serv.c.diff?r1=1.22;r2=1.23

Also note that this is a POST-authentication bug, meaning that an attacker would need to have valid credentials to successfully authenticate to the server in order to exploit this.  If a user already has the ability to log into the server, there are a number of other mechanisms that could be exploited (arguably easier) to consume excessive resources on the server.

Comment 1 Vincent Danen 2012-04-04 17:21:31 UTC

Statement:

(none)

Comment 2 Vincent Danen 2012-04-04 17:22:10 UTC

Created openssh tracking bugs for this issue

Affects: fedora-all [bug 809939]

Comment 6 errata-xmlrpc 2012-06-20 07:17:43 UTC

This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2012:0884 https://rhn.redhat.com/errata/RHSA-2012-0884.html