CVE-2025-54461 identifies an access control vulnerability in the ChatLuck communication platform developed by NEOJAPAN Inc., specifically affecting versions V6.6 R2.0 and earlier. The vulnerability arises from insufficient granularity in the mechanism that governs the invitation and registration of guest users. Normally, guest user invitations should be tightly controlled to prevent unauthorized users from gaining access. However, due to this flaw, an uninvited user can bypass intended restrictions and register themselves as a guest user without any prior authorization. The vulnerability is remotely exploitable over the network without requiring any authentication or user interaction, which increases the attack surface. The CVSS 3.0 base score is 5.3, reflecting a medium severity level, primarily due to the limited confidentiality impact and no direct effect on integrity or availability. Exploitation could allow unauthorized access to guest-level communication channels or data, potentially exposing sensitive internal discussions or information shared within the platform. No public exploits or active exploitation have been reported to date. The lack of a patch link suggests that a fix may still be pending or in development. Organizations using ChatLuck should monitor vendor communications for patches and consider interim controls such as restricting guest user invitations and monitoring guest account activity. This vulnerability highlights the importance of robust access control mechanisms in collaborative communication tools to prevent unauthorized access and data exposure.

For European organizations, the primary impact of CVE-2025-54461 is the potential unauthorized access by uninvited guest users to internal communication channels within ChatLuck. This could lead to exposure of sensitive corporate information, strategic discussions, or personal data shared in guest-accessible areas. While the vulnerability does not allow modification or disruption of data (no integrity or availability impact), the confidentiality breach could have reputational and compliance consequences, especially under GDPR regulations. Industries relying heavily on secure internal communications, such as finance, healthcare, government, and critical infrastructure, may face increased risk. The ease of exploitation without authentication means that attackers can attempt access from external networks, increasing the threat landscape. Although no known exploits exist currently, the vulnerability could be targeted in the future, particularly by threat actors seeking intelligence or insider information. European organizations should consider the risk of data leakage and unauthorized presence within their communication platforms and implement compensating controls until patches are available.

1. Monitor NEOJAPAN Inc. official channels for patches addressing CVE-2025-54461 and apply updates promptly once released. 2. Temporarily disable or restrict the guest user invitation feature in ChatLuck to prevent unauthorized registrations. 3. Implement strict monitoring and logging of guest user account creation and activity to detect suspicious behavior early. 4. Enforce network-level access controls such as IP whitelisting or VPN requirements for accessing ChatLuck, limiting exposure to external attackers. 5. Conduct regular audits of guest user permissions and remove any unnecessary or inactive guest accounts. 6. Educate internal users about the risks of sharing sensitive information in guest-accessible channels and encourage use of secure communication practices. 7. If possible, integrate ChatLuck with identity and access management (IAM) solutions to enhance guest user verification and control. 8. Review and strengthen overall access control policies within the organization’s communication platforms to ensure least privilege principles are enforced.