The Oracle Linux operating system must be configured so that the SSH daemon does not allow compression or only allows compression after successful authentication.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-221864 | OL07-00-040470 | SV-221864r991589_rule | Medium |
| Description |
| If compression is allowed in an SSH connection prior to authentication, vulnerabilities in the compression software could result in compromise of the system from an unauthenticated connection, potentially with root privileges. |
| STIG | Date |
| Oracle Linux 7 Security Technical Implementation Guide | 2024-08-26 |
Details
| Check Text (C-23579r880589_chk) |
| Note: For Oracle Linux 7.4 and above, this requirement is not applicable. Verify the SSH daemon performs compression after a user successfully authenticates. Check that the SSH daemon performs compression after a user successfully authenticates with the following command: # grep -i compression /etc/ssh/sshd_config Compression delayed If the "Compression" keyword is set to "yes", is missing, or the returned line is commented out, this is a finding. |
| Fix Text (F-23568r880590_fix) |
| Uncomment the "Compression" keyword in "/etc/ssh/sshd_config" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor) on the system and set the value to "delayed" or "no": Compression no The SSH service must be restarted for changes to take effect. |