Kanboard is project management software that focuses on the Kanban methodology. Prior to version 1.2.46, Kanboard is vulnerable to username enumeration and IP spoofing-based brute-force protection bypass. By analyzing login behavior and abusing trusted HTTP headers, an attacker can determine valid usernames and circumvent rate-limiting or blocking mechanisms. Any organization running a publicly accessible Kanboard instance is affected, especially if relying on IP-based protections like Fail2Ban or CAPTCHA for login rate-limiting. Attackers with access to the login page can exploit this flaw to enumerate valid usernames and bypass IP-based blocking mechanisms, putting all user accounts at higher risk of brute-force or credential stuffing attacks. Version 1.2.46 contains a patch for the issue.