AlmaLinux OS 9 SSH daemon must not allow compression or must only allow compression after successful authentication.

An XCCDF Rule

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.

ID: SV-269260r1050142_rule
Version: ALMA-09-020370
Severity: Medium
References: CCI-000366
Updated: about 2 months ago

Remediation Templates

Configure the SSH daemon to not allow compression.

Add the following line to "/etc/ssh/sshd_config", or uncomment the line and set the value to "delayed" or preferably "no":

Compression no
Alternatively, add the setting to an include file if the line "Include /etc/ssh/sshd_config.d/*.conf" is found at the top of the "/etc/ssh/sshd_config" file:

$ echo 'Compression no' > /etc/ssh/sshd_config.d/40-compression.conf

Restart the SSH daemon for the settings to take effect:

$ systemctl restart sshd.service

AlmaLinux OS 9 SSH daemon must not allow compression or must only allow compression after successful authentication.

Description

Remediation Templates

A Manual Procedure