Information
The Operating System (OS) must be configured in the system-auth file to prohibit password reuse for a minimum of five generations.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. If the information system or application allows the user to reuse their password consecutively when that password has exceeded its defined lifetime, the end result is a password that is not changed per policy requirements.
RHEL 8 uses "pwhistory" consecutively as a mechanism to prohibit password reuse. This is set in both:/etc/pam.d/password-auth/etc/pam.d/system-auth.
Note that manual changes to the listed files may be overwritten by the "authselect" program.
Solution
Configure the operating system in the system-auth file to prohibit password reuse for a minimum of five generations.
Add the following line in "/etc/pam.d/system-auth" (or modify the line to have the required value):
password requisite pam_pwhistory.so use_authtok remember=5 retry=3