Vulnerability Discussion

Pluggable authentication modules (PAM) allow for a modular approach to integrating authentication methods. PAM operates in a top-down processing model and if the modules are not listed in the correct order, an important security function could be bypassed if stack entries are not centralized.

Check

Verify that /etc/pam.d/passwd is configured to use /etc/pam.d/system-auth when changing passwords:

# cat /etc/pam.d/passwd | grep -i substack | grep -i system-auth
password substack system-auth

If no results are returned, the line is commented out, this is a finding.

Fix

Configure PAM to utilize /etc/pam.d/system-auth when changing passwords.

Add the following line to "/etc/pam.d/passwd" (or modify the line to have the required value):

password substack system-auth