The SSH client must be configured to not use CBC-based ciphers.

From MAC OSX 10.6 Workstation Security Technical Implementation Guide

Associated with IA controls: ECSC-1

Associated with: CCI-000366

SV-39374r1_rule The SSH client must be configured to not use CBC-based ciphers.

Vulnerability discussion

The Cipher-Block Chaining (CBC) mode of encryption as implemented in the SSHv2 protocol is vulnerable to chosen plaintext attacks and must not be used.

Check content

Open a terminal session and enter the following command. grep -i ciphers /etc/ssh_config | grep -v '^#' If no lines are returned, or the returned ciphers list contains any cipher ending with "CBC", this is a finding.

Fix text

Open a terminal session and edit the SSH client configuration file "/etc/ssh_config" and remove any ciphers ending with "CBC".

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