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OpenSSH CBC Mode Plaintext Recovery Vulnerability
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Secunia Advisory:
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SA32760
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Release Date:
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2008-11-17
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Last Update:
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2008-11-25
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Popularity:
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2,357 views
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Critical:
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Less critical
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Impact:
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Exposure of sensitive information
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Where:
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From local network
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Solution Status:
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Unpatched
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| Software: | OpenSSH 4.x
OpenSSH 5.x
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Subscribe:
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| CVE reference: | CVE-2008-5161
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Description:
A vulnerability has been reported in OpenSSH, which potentially can be exploited by malicious people to disclose sensitive information.
The vulnerability is caused due to the improper handling of errors within an SSH session encrypted with a block cipher algorithm in the CBC (Cipher-Block Chaining) mode. This can be exploited to potentially disclose up to 32 plaintext bits from an arbitrary block of ciphertext.
NOTE: An attack has a low probability of success, an attempt resulting in the termination of the current SSH session.
Successful exploitation requires that an attacker is able to read and alter network data.
This is related to:
SA32740
The vulnerability is reported in version 4.7p1. Other versions may also be affected.
Solution:
Allow only CTR (Counter) mode cipher algorithms (e.g. AES-CTR) to be used in an SSH session.
Provided and/or discovered by:
Martin Albrecht, Kenny Paterson, and Gaven Watson from the Information Security Group at Royal Holloway, University of London, reported via CPNI
Changelog:
2008-11-21: Added CVE reference. Added "OpenSSH 5.x" to the list of affected products. Updated "Original Advisory" section with vendor advisory.
2008-11-25: Added link to US-CERT.
Original Advisory:
Centre for the Protection of National Infrastructure (CPNI):
http://www.cpni.gov.uk/Docs/Vulnerability_Advisory_SSH.txt
OpenSSH:
http://openssh.org/txt/cbc.adv
Other References:
SA32740:
http://secunia.com/advisories/32740/
US-CERT VU#958563:
http://www.kb.cert.org/vuls/id/958563
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About this Secunia Advisory
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Please note: The information that this Secunia Advisory is based on comes from a third party unless stated otherwise.
Secunia collects, validates, and verifies all vulnerability reports issued by security research groups, vendors, and others.
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