CVE-2026-25509 identifies an email enumeration vulnerability in ci4ms, a CMS skeleton built on the CodeIgniter 4 framework. The vulnerability arises from an observable response discrepancy during the password reset workflow, where the system’s responses differ based on whether an email address is registered. This behavior allows unauthenticated attackers to confirm the existence of user accounts by analyzing subtle differences in server responses, such as timing, error messages, or response content. The vulnerability is classified under CWE-204 (Observable Response Discrepancy) and affects all ci4ms versions prior to 0.28.5.0. Since the attack vector is network-based and requires no privileges or user interaction, it is relatively easy to exploit. The impact is limited to confidentiality as it leaks user registration information but does not allow direct account compromise or system manipulation. The issue has been addressed in ci4ms version 0.28.5.0 by standardizing responses during password reset requests to prevent enumeration. No public exploits have been reported yet, but the vulnerability can facilitate further attacks such as targeted phishing, credential stuffing, or social engineering by revealing valid user emails.

For European organizations, this vulnerability primarily threatens the confidentiality of user data by exposing registered email addresses. Attackers can leverage this information to craft more convincing phishing campaigns or attempt brute-force attacks on known accounts, increasing the risk of account compromise indirectly. Organizations relying on ci4ms for internal or external-facing portals may face reputational damage if user data is leaked or abused. While the vulnerability does not directly affect system integrity or availability, the reconnaissance advantage it provides can be a stepping stone for more severe attacks. Given the widespread use of CMS platforms in Europe across various sectors including government, education, and private enterprises, the potential for targeted attacks increases. Organizations with sensitive user bases or regulatory obligations under GDPR must treat this vulnerability seriously to avoid compliance issues related to unauthorized data disclosure.

European organizations using ci4ms should immediately upgrade to version 0.28.5.0 or later, where the vulnerability is patched. If upgrading is not immediately feasible, implement application-layer mitigations such as uniform response messages and timing controls during password reset requests to eliminate observable discrepancies. Employ rate limiting and CAPTCHA challenges on password reset endpoints to hinder automated enumeration attempts. Monitor logs for abnormal password reset request patterns that may indicate enumeration activity. Additionally, educate users about phishing risks and encourage strong, unique passwords combined with multi-factor authentication (MFA) to reduce the impact of potential account enumeration. Regularly audit and update CMS components and dependencies to ensure timely application of security patches. Finally, consider implementing Web Application Firewalls (WAFs) with rules designed to detect and block enumeration behaviors specific to ci4ms password reset flows.