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The SSH daemon must not allow compression or must only allow compression after successful authentication.


Overview

Finding ID Version Rule ID IA Controls Severity
V-22488 GEN005539 SV-64089r1_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 5 Security Technical Implementation Guide 2018-03-01

Details

Check Text ( C-52515r2_chk )
Check the SSH daemon configuration for the compression setting.

# grep -i Compression /etc/ssh/sshd_config | egrep "no|delayed"

If the setting is missing or is commented out, this is a finding.

If the setting is present but is not set to "no" or "delayed", this is a finding.
Fix Text (F-54627r1_fix)
Edit the SSH daemon configuration and add or edit the "Compression" setting value to "no" or "delayed".

Restart the SSH daemon.
# /sbin/service sshd restart