OL 9 SSH daemon must disable remote X connections for interactive users.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-271713 | OL09-00-002350 | SV-271713r1091851_rule | CCI-000366 | medium |
| Description | ||||
| When X11 forwarding is enabled, there may be additional exposure to the server and client displays if the SSHD proxy display is configured to listen on the wildcard address. By default, SSHD binds the forwarding server to the loopback address and sets the hostname part of the DISPLAY environment variable to localhost. This prevents remote hosts from connecting to the proxy display. | ||||
| STIG | Date | |||
| Oracle Linux 9 Security Technical Implementation Guide | 2025-05-08 | |||
Related Frameworks
4 paths across 3 frameworks
Related Frameworks
NIST 800-531 mapping
CM-6
1.00
- DISA · 1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
NIST 800-1712 mappings
3.4.1
1.00
- DISA · 1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
3.4.2
1.00
- DISA · 1 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
CCI1 mapping
CCI-000366
1.00
- DISA · 1 · disa_xccdf · related
Details
Check Text (C-271713r1091851_chk)
Verify that OL 9 SSH daemon does not allow X11Forwarding with the following command:
$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*x11forwarding'
X11forwarding no
If the value is returned as "yes", the returned line is commented out, or no output is returned, and X11 forwarding is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.
Fix Text (F-75670r1091850_fix)
Configure the SSH daemon to not allow X11 forwarding.
Add the following line to "/etc/ssh/sshd_config" or to a file in "/etc/ssh/sshd_config.d" or uncomment the line and set the value to "no":
X11Forwarding no
The SSH service must be restarted for changes to take effect:
$ sudo systemctl restart sshd.service