GNU Mailman 2.1.39, as bundled in cPanel (and WHM), allows unauthenticated attackers to read arbitrary files via ../ directory traversal at /mailman/private/mailman (aka the private archive authentication endpoint) via the username parameter. NOTE: multiple third parties report that they are unable to reproduce this, regardless of whether cPanel or WHM is used.
CWE-24, CWE-22