OpenSSH CBC Mode Error Handling May Let Certain Remote Users Obtain Plain Text in Certain Cases
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SecurityTracker Alert ID: 1021235
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SecurityTracker URL: http://securitytracker.com/id?1021235
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CVE Reference: CVE-2008-5161
(Links to External Site)
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Updated: Nov 21 2008
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Original Entry Date: Nov 17 2008
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Impact: Disclosure of user information
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Vendor Confirmed: Yes
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Version(s): 4.7p1, possibly other versions
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Description: A vulnerability was reported in OpenSSH. A remote user with control of the network can obtain portions of plain text in certain cases.
A remote user with control of the network between the client and the server can inject connection errors and monitor the SSH error
handling response to recover up to 32 bits of plain text from an SSH-protected connection.
The attack process will terminate
the SSH connection.
CBC mode connections are affected.
CTR mode connections are not affected.
Martin Albrecht, Kenny Paterson
and Gaven Watson from the Information Security Group at Royal Holloway, University of London reported this vulnerability via the
Centre for the Protection of National Infrastructure (CPNI).
The original advisory is available at:
http://www.cpni.gov.uk/Docs/Vulnerability_Advisory_SSH.txt
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Impact: A remote user with control of the network can obtain portions of plain text in certain cases.
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Solution: No solution was available at the time of this entry.
The vendor notes that AES CTR mode and arcfour ciphers are not affected and
may be preferentially selected by placing the following directive in sshd_config and ssh_config:
Ciphers aes128-ctr,aes256-ctr,arcfour256,arcfour,aes128-cbc,aes256-cbc
The vendor's advisory is available at:
http://www.openssh.org/txt/cbc.adv
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Vendor URL: www.openssh.org/txt/cbc.adv (Links to External Site)
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Cause: Randomization error
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Underlying OS: Linux (Any), UNIX (Any)
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Message History:
None.
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Source Message Contents
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Date: Mon, 17 Nov 2008 07:44:32 -0500
Subject: OpenSSH
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http://www.cpni.gov.uk/Docs/Vulnerability_Advisory_SSH.txt
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