Permissions, Privileges, and Access Controls in OpenSSH

1) Permissions, Privileges, and Access Controls

EUVDB-ID: #VU33288

Risk: High

CVSSv3.1: 7.1 [CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2015-5600

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to #BASIC_IMPACT#.

The kbdint_next_device function in auth2-chall.c in sshd in OpenSSH through 6.9 does not properly restrict the processing of keyboard-interactive devices within a single connection, which makes it easier for remote attackers to conduct brute-force attacks or cause a denial of service (CPU consumption) via a long and duplicative list in the ssh -oKbdInteractiveDevices option, as demonstrated by a modified client that provides a different password for each pam element on this list.

Mitigation

Install update from vendor's website.

Vulnerable software versions

OpenSSH: 6.0 - 6.9

External links

http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/auth2-chall.c
http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/auth2-chall.c.diff?r1=1.42&r2=1.43&f=h
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10697
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-August/165170.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-July/162955.html
http://lists.opensuse.org/opensuse-security-announce/2015-09/msg00017.html
http://openwall.com/lists/oss-security/2015/07/23/4
http://rhn.redhat.com/errata/RHSA-2016-0466.html
http://seclists.org/fulldisclosure/2015/Jul/92
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html
http://www.oracle.com/technetwork/topics/security/bulletinoct2015-2511968.html
http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
http://www.securityfocus.com/bid/75990
http://www.securityfocus.com/bid/91787
http://www.securityfocus.com/bid/92012
http://www.securitytracker.com/id/1032988
http://www.ubuntu.com/usn/USN-2710-1
http://www.ubuntu.com/usn/USN-2710-2
http://h20564.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c04952480
http://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05128992
http://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05157667
http://kc.mcafee.com/corporate/index?page=content&id=SB10136
http://kc.mcafee.com/corporate/index?page=content&id=SB10157
http://lists.debian.org/debian-lts-announce/2018/09/msg00010.html
http://security.gentoo.org/glsa/201512-04
http://security.netapp.com/advisory/ntap-20151106-0001/
http://support.apple.com/kb/HT205031

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.