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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-37830r1_rule ECSC-1 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
Red Hat Enterprise Linux 5 Security Technical Implementation Guide 2015-03-12

Details

Check Text ( C-37030r1_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-32298r2_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.