CVE-2025-40676: BBMRI-ERIC Negotiator Auth Bypass IDOR

CVE-2025-40676 Overview

CVE-2025-40676 is an Insecure Direct Object Reference (IDOR) vulnerability in the BBMRI-ERIC Negotiator v3.15.2 application. The Biobanking and Biomolecular Resources European Research Infrastructure Consortium (BBMRI-ERIC) maintains this platform for coordinating biobank access requests. The flaw resides in the /api/v3/users/<userID> endpoint, where the application fails to verify that the authenticated user is authorized to access the requested userID resource. An attacker with valid low-privilege credentials can manipulate the userID path parameter to read or modify data belonging to other users. The issue is classified under [CWE-639]: Authorization Bypass Through User-Controlled Key.

Critical Impact
Authenticated attackers can enumerate and tamper with other users' account data by iterating the userID parameter, exposing personally identifiable information tied to biobank research participants and staff.

Affected Products

BBMRI-ERIC Negotiator v3.15.2
Deployments exposing the /api/v3/users/<userID> endpoint
Downstream biobank portals integrating the Negotiator v3 API

Discovery Timeline

2025-10-07 - CVE-2025-40676 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-40676

Vulnerability Analysis

The Negotiator v3 REST API exposes user records through the /api/v3/users/<userID> route. The handler resolves the userID value directly from the request path and returns or updates the matching record without validating that the caller owns the resource or holds an administrative role. An authenticated user can therefore substitute another account identifier and receive that account's stored attributes. Because the endpoint accepts modification requests using the same identifier scheme, the flaw enables both information disclosure and data tampering. The vulnerability requires only low-privilege authentication and no user interaction, and it is exploitable over the network against any reachable Negotiator instance.

Root Cause

The root cause is missing object-level authorization on user resources. The application trusts the client-supplied userID as a lookup key without cross-referencing it against the session principal or a role-based access policy. This pattern maps directly to [CWE-639] and to the OWASP API Security Top 10 category BOLA (Broken Object Level Authorization).

Attack Vector

An attacker first obtains a valid Negotiator account, which may be provisioned through standard user registration flows depending on deployment. The attacker then issues authenticated HTTP GET or PUT requests to /api/v3/users/<userID>, incrementing or fuzzing the userID value to enumerate accounts. Successful responses return other users' profile data, which may include contact details, organizational affiliations, and role assignments. Modification requests permit the attacker to alter fields on foreign accounts, potentially enabling downstream privilege escalation or social engineering.

No public proof-of-concept exploit code has been released. Refer to the INCIBE Security Notice for coordinated disclosure details.

Detection Methods for CVE-2025-40676

Indicators of Compromise

Sequential or high-volume authenticated requests to /api/v3/users/ with varying numeric userID values from a single session or source IP.
HTTP PUT or PATCH requests to /api/v3/users/<userID> where the userID does not match the authenticated session's owner identifier.
Application logs showing successful 2xx responses on user endpoints for identifiers the session should not be able to access.

Detection Strategies

Correlate authenticated session identifiers with the userID path parameter and alert when they diverge outside of administrative role contexts.
Deploy web application firewall (WAF) rules that rate-limit sequential access to /api/v3/users/ endpoints from a single principal.
Baseline normal API access patterns per user role and flag deviations, particularly enumeration-style traversal of the user resource.

Monitoring Recommendations

Forward Negotiator API access logs to a centralized analytics platform and retain them for retrospective IDOR hunting.
Instrument the application to emit an authorization-decision log entry for every user resource access, including subject, target userID, and decision outcome.
Review audit trails for unexpected modifications to user profile fields, especially role or email address changes.

How to Mitigate CVE-2025-40676

Immediate Actions Required

Restrict network exposure of the Negotiator v3 API to trusted networks or authenticated reverse proxies until a patched release is deployed.
Audit existing user accounts for unauthorized profile changes, particularly to email addresses, roles, and organizational affiliations.
Rotate credentials and session tokens for any accounts that show signs of tampering in access logs.

Patch Information

Consult the INCIBE Security Notice for the current list of fixed Negotiator releases and upgrade guidance from BBMRI-ERIC. Upgrade beyond v3.15.2 to a version in which object-level authorization has been enforced on /api/v3/users/<userID>.

Workarounds

Place an API gateway in front of Negotiator that validates the session principal against the requested userID and rejects mismatches for non-administrative users.
Disable or gate self-service registration to reduce the pool of attackers able to obtain the low-privilege credentials required for exploitation.
Apply WAF signatures that block unauthenticated or anomalous access patterns to the /api/v3/users/ route family.

bash

# Example NGINX snippet to restrict the vulnerable endpoint to an allow-listed admin network
location ~ ^/api/v3/users/[0-9]+$ {
    allow 10.0.0.0/24;   # admin subnet
    deny  all;
    proxy_pass http://negotiator_backend;
}