The SSH client must be configured to not use CBC-based ciphers.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-39402 | SRG-OS-000157-ESXI5 | SV-51260r2_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 |
|---|---|
| VMware ESXi Server 5.0 Security Technical Implementation Guide | 2017-01-06 |
Details
| Check Text ( C-46676r2_chk ) |
|---|
| Disable lock down mode. Enable the ESXi Shell. Check the SSH client configuration for allowed ciphers. # grep -i ciphers /etc/ssh/ssh_config | grep -v '^#' Re-enable lock down mode. If the returned ciphers list contains any cipher ending with cbc, this is a finding. If the /etc/ssh/ssh_config file does not exist or the Ciphers option is not set, this is not a finding. |
| Fix Text (F-44415r1_fix) |
|---|
| Disable lock down mode. Enable the ESXi Shell. Edit the SSH client configuration and add/modify the "Ciphers" configuration (examples of disallowed ciphers: aes128-cbc, aes192-cbc, aes256-cbc, arcfour256blowfish-cbc, cast128-cbc, 3des-cbc). # vi /etc/ssh/ssh_config Re-enable lock down mode. |