CVE-2025-59113 identifies a security vulnerability in Windu CMS version 4.1 related to improper restriction of excessive authentication attempts (CWE-307). The CMS attempts to mitigate brute-force attacks by using a client-side parameter named loginError to track the number of failed login attempts or to enforce timeouts. However, this parameter is managed solely on the client side and is not validated or stored on the server. As a result, an attacker can reset or manipulate the loginError parameter to bypass the brute-force protection mechanism entirely. This flaw allows unlimited password guessing attempts without triggering any server-side lockout or delay, significantly increasing the risk of successful credential brute forcing. The vulnerability is remotely exploitable without requiring any authentication or user interaction, increasing its attack surface. The CVSS 4.0 base score is 6.9 (medium severity), reflecting the network attack vector, low attack complexity, and no privileges or user interaction needed, but limited impact on confidentiality and no impact on integrity or availability. The vulnerability was confirmed only in version 4.1 and was fixed in build 2250 of that version. No public exploits have been reported to date. The root cause is the reliance on client-side state for security-critical functionality, which is a known anti-pattern in secure authentication design. Proper mitigation involves server-side tracking of failed login attempts and enforcement of lockouts or delays.

For European organizations using Windu CMS version 4.1 prior to build 2250, this vulnerability exposes them to credential brute-force attacks that can lead to unauthorized access to administrative or user accounts. Successful exploitation could allow attackers to compromise sensitive data, modify website content, or use the CMS as a foothold for further network intrusion. Given the CMS’s role in managing web content, exploitation could also result in defacement, data leakage, or disruption of online services. The lack of server-side enforcement means brute-force attacks can be automated at scale, increasing the risk of credential stuffing or password spraying campaigns. Organizations in sectors with high regulatory requirements for data protection (e.g., finance, healthcare, government) face increased compliance risks if breaches occur. Although no known exploits are currently active, the vulnerability’s ease of exploitation and remote accessibility make it a significant threat if left unpatched. The impact is primarily on confidentiality and access control, with limited direct impact on system integrity or availability.

European organizations should immediately upgrade Windu CMS installations to version 4.1 build 2250 or later, where this vulnerability is fixed. If immediate patching is not feasible, implement server-side brute-force protections such as rate limiting login attempts per IP address or user account, and enforce account lockouts or progressive delays after multiple failed attempts. Deploy Web Application Firewalls (WAFs) with rules to detect and block brute-force patterns targeting login endpoints. Enable multi-factor authentication (MFA) for all CMS user accounts to reduce the risk of compromised credentials leading to unauthorized access. Regularly monitor authentication logs for unusual login failure patterns and investigate potential brute-force activity. Educate administrators and users on strong password policies and the risks of credential reuse. Conduct penetration testing and vulnerability assessments to verify the effectiveness of mitigations. Finally, review CMS configurations to ensure no other client-side security controls are relied upon for critical protections.