CVE-2025-65899 identifies a user enumeration vulnerability in Kalmia CMS version 0.2.0. The core issue lies in the authentication mechanism, which returns distinct error messages depending on whether the username is invalid ('user_not_found') or the password is incorrect for a valid username ('invalid_password'). This difference in responses allows unauthenticated attackers to enumerate valid usernames by submitting login attempts and analyzing the error messages returned. User enumeration vulnerabilities do not directly compromise passwords or system integrity but significantly aid attackers in crafting targeted brute-force attacks, phishing campaigns, or social engineering exploits by providing a list of valid user accounts. The vulnerability does not require authentication or user interaction beyond submitting login attempts. No patches or fixes have been linked yet, and no known exploits have been reported in the wild as of the publication date. The lack of a CVSS score means severity must be assessed based on impact and exploitability factors. The vulnerability primarily affects confidentiality by exposing valid usernames, which can be a critical first step in multi-stage attacks. The affected version is specifically Kalmia CMS 0.2.0, a content management system likely used by organizations for website or application management. The vulnerability was reserved and published in late 2025, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a risk primarily to the confidentiality of user information. By enabling attackers to enumerate valid usernames, it lowers the barrier for subsequent attacks such as password guessing, credential stuffing, or phishing. Organizations in sectors with high-value targets—such as government, finance, healthcare, and critical infrastructure—may face increased risk if Kalmia CMS is used in their environments. The vulnerability does not directly impact system integrity or availability but can be a stepping stone for more severe attacks. The absence of known exploits reduces immediate risk, but the ease of exploitation and the commonality of user enumeration attacks mean that organizations should not underestimate the threat. The impact is amplified if usernames correspond to privileged accounts or if password policies are weak. Additionally, GDPR considerations mean that exposing user identity information could have regulatory implications if it leads to data breaches or unauthorized access.

European organizations using Kalmia CMS 0.2.0 should implement the following mitigations: 1) Standardize authentication error messages so that responses do not reveal whether a username exists, returning a generic message such as 'Invalid username or password' for all failed login attempts. 2) Implement rate limiting and account lockout policies to reduce the feasibility of automated enumeration and brute-force attacks. 3) Monitor authentication logs for suspicious login attempts indicative of enumeration or brute-force activity. 4) Apply web application firewalls (WAFs) with rules designed to detect and block enumeration patterns. 5) Encourage or enforce multi-factor authentication (MFA) to reduce the impact of compromised credentials. 6) Keep the CMS and all related components updated and monitor for official patches or advisories from Kalmia CMS developers. 7) Conduct regular security assessments and penetration tests to identify similar vulnerabilities. 8) Educate users and administrators about phishing risks and the importance of strong, unique passwords. These steps go beyond generic advice by focusing on specific controls tailored to the nature of the vulnerability and the affected product.