Title

The SSH daemon must be configured to not use CBC ciphers. (Cat II impact)

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 ciphers /etc/sshd_config 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 daemon configuration file "/etc/sshd_config" and remove any ciphers ending with "CBC". If necessary, add a Ciphers line.

Additional Identifiers

Rule ID: SV-39364r1_rule

Vulnerability ID: V-22459

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.