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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-22462	GEN005511	SV-63595r1_rule		Medium

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

STIG	Date
Oracle Linux 5 Security Technical Implementation Guide	2020-02-25

Details

Check Text ( C-52247r2_chk )
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 (F-54201r1_fix)
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.