CVE-2025-65899 identifies a user enumeration vulnerability in the authentication mechanism of Kalmia CMS version 0.2.0. The core issue arises because the system returns different error messages depending on whether the username is invalid (user_not_found) or the password is incorrect (invalid_password). This behavior allows an unauthenticated attacker to distinguish valid usernames from invalid ones by observing the system's responses during login attempts. User enumeration vulnerabilities fall under CWE-204 and are significant because they can provide attackers with a list of valid usernames, which can then be used to launch more focused attacks such as password guessing, credential stuffing, or social engineering. The vulnerability has a CVSS v3.1 base score of 5.3, indicating medium severity. The vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N shows that the attack can be performed remotely over the network without privileges or user interaction, and it impacts confidentiality to a limited extent by revealing valid usernames. There is no impact on integrity or availability. No patches or fixes are currently linked, and no known exploits have been reported in the wild as of the publication date (December 4, 2025). The vulnerability is particularly relevant for organizations that rely on Kalmia CMS for web content management and have public-facing login portals, as attackers can leverage this flaw to gather intelligence on valid user accounts.

For European organizations, the primary impact of CVE-2025-65899 is the exposure of valid usernames through user enumeration, which can facilitate subsequent targeted attacks such as brute-force password attempts or phishing campaigns. While the vulnerability does not directly compromise data confidentiality, integrity, or availability, the disclosure of valid usernames can significantly lower the barrier for attackers to compromise accounts, especially if weak or reused passwords are present. Organizations in sectors with high-value targets, such as finance, government, healthcare, and critical infrastructure, could face increased risk if attackers use enumerated usernames to gain unauthorized access. Additionally, public-facing Kalmia CMS instances in Europe could be targeted to harvest user information, potentially leading to reputational damage and compliance issues under regulations like GDPR if user data is indirectly exposed or abused. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits based on this vulnerability.

To mitigate CVE-2025-65899, organizations should implement the following specific measures: 1) Standardize authentication error messages so that responses for invalid usernames and incorrect passwords are indistinguishable, preventing attackers from differentiating valid users. 2) Implement account lockout or progressive delay mechanisms after multiple failed login attempts to reduce the feasibility of automated enumeration and brute-force attacks. 3) Employ rate limiting and IP throttling on authentication endpoints to limit the speed of enumeration attempts. 4) Monitor authentication logs for unusual patterns indicative of enumeration or brute-force activity and trigger alerts for investigation. 5) If possible, upgrade to a patched version of Kalmia CMS once available or apply custom patches to address the vulnerability. 6) Educate users about strong, unique passwords and consider multi-factor authentication (MFA) to reduce the risk of account compromise even if usernames are known. 7) Conduct regular security assessments and penetration tests focusing on authentication mechanisms to detect similar issues proactively.