CVE-2025-59116 identifies a user enumeration vulnerability in Windu CMS version 4.1, classified under CWE-204 (Observable Response Discrepancy). The flaw arises during the authentication process where the system returns different error messages or response behaviors depending on whether the username exists. This discrepancy enables an unauthenticated remote attacker to confirm valid usernames by analyzing the system's responses to login attempts. Once valid usernames are identified, attackers can launch targeted brute force attacks to compromise accounts. The vulnerability has a CVSS 4.0 base score of 6.9 (medium severity), reflecting its network attack vector, low complexity, no privileges or user interaction required, and limited impact confined to confidentiality (user enumeration). The issue was confirmed in Windu CMS 4.1 and resolved in build 2250 of the same version. No public exploits have been reported yet. The vulnerability's exploitation could lead to unauthorized access if combined with weak password policies or other security weaknesses. Windu CMS is a content management system used primarily for website management, and this vulnerability affects the login module's error handling logic.

For European organizations, this vulnerability primarily threatens the confidentiality of user account information by enabling attackers to enumerate valid usernames. This can facilitate subsequent brute force or credential stuffing attacks, potentially leading to unauthorized access to administrative or user accounts. Organizations relying on Windu CMS for public-facing websites or internal portals may face increased risk of account compromise, data breaches, or service disruption if attackers leverage this flaw. The impact is heightened in sectors with sensitive data or critical infrastructure managed via Windu CMS, such as government agencies, educational institutions, or SMEs with limited cybersecurity resources. While the vulnerability does not directly affect system integrity or availability, successful exploitation can serve as a stepping stone for deeper attacks. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers often weaponize such enumeration flaws rapidly after disclosure.

European organizations using Windu CMS version 4.1 should immediately upgrade to version 4.1 build 2250 or later, where the vulnerability is fixed. If upgrading is not immediately feasible, implement the following mitigations: (1) Standardize login error messages to be generic and indistinguishable regardless of username validity to prevent response-based user enumeration. (2) Enforce strong account lockout or throttling policies after multiple failed login attempts to hinder brute force attacks. (3) Deploy web application firewalls (WAFs) with rules to detect and block suspicious login patterns indicative of enumeration or brute force. (4) Monitor authentication logs for unusual login attempts or spikes in failed authentications. (5) Educate users and administrators on strong password practices and multi-factor authentication (MFA) to reduce the risk of account compromise. (6) Conduct regular security assessments of CMS installations to identify and remediate similar flaws proactively.