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 login process where the system returns different messages or responses depending on whether the username exists or not. This discrepancy enables an attacker to confirm valid usernames without authentication or user interaction, facilitating brute force attacks against valid accounts. The vulnerability is remotely exploitable over the network with low attack complexity and no privileges required. The vendor was notified early but has not provided detailed information or patches, and only version 4.1 has been tested and confirmed vulnerable. The CVSS 4.0 base score is 6.9 (medium severity), reflecting the network attack vector, no required privileges or user interaction, and limited impact confined to confidentiality (user enumeration). While no known exploits are reported in the wild, the vulnerability increases the risk of credential stuffing and brute force attacks that could lead to unauthorized access. The absence of patches necessitates defensive measures such as uniform error handling and login attempt restrictions. Given Windu CMS's use in web content management, this vulnerability could expose websites to account compromise and subsequent data breaches or defacements.

For European organizations using Windu CMS 4.1, this vulnerability poses a significant risk to the confidentiality of user credentials and the integrity of authentication mechanisms. Successful exploitation allows attackers to identify valid usernames, which can be leveraged in brute force or credential stuffing attacks to gain unauthorized access. This can lead to data breaches, website defacement, or further exploitation of compromised accounts. Organizations in sectors with sensitive data or critical web infrastructure are particularly vulnerable. The lack of vendor patches increases exposure duration, and attackers may target European entities due to the region's extensive use of CMS platforms. Additionally, regulatory frameworks like GDPR impose strict requirements on protecting user data, so exploitation could result in compliance violations and financial penalties. The vulnerability's network accessibility and no requirement for authentication make it easier for remote attackers to exploit, increasing the threat surface for European enterprises.

1. Implement uniform error messages during login attempts to prevent attackers from distinguishing valid usernames from invalid ones. 2. Deploy rate limiting and account lockout mechanisms after a defined number of failed login attempts to hinder brute force attacks. 3. Monitor authentication logs for unusual login patterns or repeated failed attempts to detect potential enumeration or brute force activity early. 4. If possible, upgrade to a newer, patched version of Windu CMS once available or apply vendor-recommended fixes promptly. 5. Employ multi-factor authentication (MFA) to reduce the risk of account compromise even if credentials are exposed. 6. Consider implementing web application firewalls (WAFs) with rules to detect and block enumeration and brute force attack patterns. 7. Educate users and administrators about the risks of weak passwords and encourage strong password policies. 8. Conduct regular security assessments and penetration tests focusing on authentication mechanisms to identify similar issues proactively.