CVE-2025-40649 is a stored Cross-Site Scripting (XSS) vulnerability identified in version 3.15.2 of the BBMRI-ERIC Negotiator, a web-based platform used by the European biobanking and biomolecular research community to facilitate negotiation and collaboration. The vulnerability stems from improper neutralization of user-supplied input in the 'text' parameter of POST requests sent to the endpoint '/api/v3/negotiations/<postUID>/posts'. Specifically, the application fails to properly validate or sanitize this input before storing and subsequently rendering it in web pages viewed by authenticated users. This flaw allows an attacker with at least authenticated access to submit malicious JavaScript payloads that are stored on the server and executed in the browsers of other users who view the affected content. The exploitation does not require elevated privileges beyond authentication, and no user interaction beyond viewing the malicious content is necessary. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), user interaction required (UI:P), and limited scope and impact on confidentiality, integrity, and availability, resulting in a medium severity score of 5.1. While no known exploits are currently reported in the wild, the vulnerability poses a risk of session cookie theft, potentially leading to session hijacking and unauthorized access to sensitive biomedical research data. The BBMRI-ERIC Negotiator is a critical tool within the European research infrastructure, making this vulnerability relevant to organizations involved in biobanking and biomolecular resource management.

For European organizations, particularly those engaged in biomedical research and biobanking, this vulnerability threatens the confidentiality and integrity of user sessions and sensitive research data. Successful exploitation could allow attackers to hijack authenticated sessions, leading to unauthorized access to negotiation details, personal data, or intellectual property. This could undermine trust in collaborative research platforms and potentially disrupt ongoing research activities. Given the specialized nature of BBMRI-ERIC Negotiator, the impact is concentrated but significant for affected entities. The vulnerability could also facilitate lateral movement within networks if attackers leverage stolen sessions to escalate privileges or access additional resources. Although availability impact is minimal, the reputational damage and regulatory implications related to data protection (e.g., GDPR) could be substantial for European institutions.

1. Implement strict server-side input validation and sanitization for the 'text' parameter to ensure that no executable scripts can be stored or rendered. 2. Apply context-aware output encoding (e.g., HTML entity encoding) when displaying user-generated content to prevent script execution. 3. Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in the browser. 4. Enforce secure cookie attributes such as HttpOnly and Secure to reduce the risk of cookie theft via XSS. 5. Monitor and audit logs for suspicious POST requests to the vulnerable endpoint to detect potential exploitation attempts. 6. Educate users to be cautious when interacting with negotiation posts and to report suspicious content. 7. Coordinate with BBMRI-ERIC to obtain and apply official patches or updates addressing this vulnerability as soon as they become available. 8. Consider implementing multi-factor authentication (MFA) to mitigate the impact of session hijacking. 9. Conduct regular security assessments and penetration tests focusing on web application vulnerabilities within the platform.