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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-22459	GEN005506	SV-46010r2_rule		Medium

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

STIG	Date
SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide	2018-09-19

Details

Check Text ( C-43291r1_chk )
Check the SSH daemon configuration for allowed ciphers. # grep -i ciphers /etc/ssh/sshd_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-39374r2_fix)
Edit the SSH daemon configuration and remove any ciphers ending with "cbc". If necessary, add a "Ciphers" line. Restart the SSH daemon. # /sbin/service sshd restart