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-63211	ESXI-06-000021	SV-77701r1_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
VMware vSphere ESXi 6.0 Security Technical Implementation Guide	2019-01-04

Details

Check Text ( C-63945r1_chk )
To verify the Compression setting, run the following command: # grep -i "^Compression" /etc/ssh/sshd_config If there is no output or the output is not exactly "Compression no", this is a finding.

Fix Text (F-69129r1_fix)
To set the Compression setting, add or correct the following line in "/etc/ssh/sshd_config": Compression no