OpenSSH 'KbdInteractiveDevices' Lets Remote Users Bypass Security Restrictions on the Target System
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SecurityTracker Alert ID: 1032988 |
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SecurityTracker URL: http://securitytracker.com/id/1032988
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CVE Reference:
CVE-2015-5600
(Links to External Site)
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Updated: Aug 12 2015
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Original Entry Date: Jul 20 2015
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Impact:
Host/resource access via network
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Fix Available: Yes Vendor Confirmed: Yes Exploit Included: Yes
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Description:
A vulnerability was reported in OpenSSH. A remote user can bypass authentication attempt limits on the target system.
A remote user can request the keyboard-interactive authentication option ('KbdInteractiveDevices') to open a large number of keyboard-interactive devices on the target server and perform a brute-force password guessing attack against the target sshd service. The number of password attempts can effectively exceed the 'MaxAuthTries' limit and are permitted to occur until the 'LoginGraceTime' limit is reached or the number of keyboard-interactive devices are used.
Servers that have keyboard-interactive authentication enabled (e.g., FreeBSD in the default configuration) are affected.
A demonstration exploit command is provided:
ssh -l[username] -oKbdInteractiveDevices=`perl -e 'print "pam," x 10000'` [target]
The original advisory is available at:
https://kingcope.wordpress.com/2015/07/16/openssh-keyboard-interactive-authentication-brute-force-vulnerability-maxauthtries-bypass/
kingcope reported this vulnerability.
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Impact:
A remote user can bypass authentication attempt limits on the target system.
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Solution:
The vendor has issued a fix (7.0).
The vendor's advisory is available at:
http://www.openssh.com/txt/release-7.0
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Vendor URL: www.openssh.com/txt/release-7.0 (Links to External Site)
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Cause:
Access control error, State error
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Underlying OS: Linux (Any), UNIX (Any), Windows (Any)
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Message History:
This archive entry has one or more follow-up message(s) listed below.
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Source Message Contents
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[Original Message Not Available for Viewing]
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