The SSH client must be configured to not use Cipher-Block Chaining (CBC)-based ciphers.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000366

SV-63595r1_rule The SSH client must be configured to not use Cipher-Block Chaining (CBC)-based ciphers.

Vulnerability discussion

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

Check content

Check the SSH client configuration for allowed ciphers. # grep -i ciphers /etc/ssh/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

Edit the SSH client configuration and remove any ciphers not starting with "3des" or "aes" and remove any ciphers ending with "cbc". If necessary, add a "Ciphers" line.

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