CVE-2025-59034: Cern Indico Auth Bypass Vulnerability

CVE-2025-59034 Overview

CVE-2025-59034 is a broken access control vulnerability in Indico, an open-source event management system developed by CERN. Indico uses Flask-Multipass, a multi-backend authentication framework for Flask applications. A legacy API endpoint intended to retrieve user details fails to properly enforce access checks. Authenticated users without administrative permissions can query the endpoint to retrieve profile details of arbitrary other users. The issue affects all versions prior to 3.3.8. The vulnerability is classified under CWE-639: Authorization Bypass Through User-Controlled Key.

Critical Impact
Any authenticated Indico user can retrieve profile details of other users through a legacy API, exposing personal data without administrative privileges.

Affected Products

CERN Indico versions prior to 3.3.8
Deployments using the Flask-Multipass legacy user details API
Self-hosted Indico instances exposing the affected endpoint to authenticated users

Discovery Timeline

2025-09-10 - CVE-2025-59034 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-59034

Vulnerability Analysis

Indico exposes a legacy API originally designed to return user profile information. The endpoint performs authentication checks but does not verify that the requesting user has authorization to view the target user's data. Any authenticated account can supply another user's identifier and receive profile details in response. This behavior falls under Insecure Direct Object Reference, a common form of broken access control tracked as CWE-639.

The scope of exposure is limited to information disclosure. The endpoint does not permit modification or account takeover, and no elevation of privilege occurs. However, Indico is widely deployed for conferences and workshops at academic and research institutions, where user profiles may include email addresses, affiliations, and other personal data subject to data protection regulations.

Root Cause

The root cause is a missing authorization check in the legacy user details API. The endpoint validates the session but does not confirm that the caller holds administrative privileges or that the caller is the owner of the requested profile. Access control logic was likely inherited from an earlier API contract that assumed administrative-only reachability.

Attack Vector

Exploitation requires an authenticated Indico account with network access to the application. An attacker iterates through user identifiers and issues API requests to the legacy endpoint. Each response returns profile fields belonging to the queried user. No user interaction and no elevated privileges are required beyond a standard account. See the GitHub Security Advisory GHSA-4269-mcfh-cp7q for maintainer details.

Detection Methods for CVE-2025-59034

Indicators of Compromise

Unusual volumes of requests from a single authenticated session to the legacy user details API endpoint
Sequential or enumerated user identifiers in access logs targeting the affected route
Requests to the legacy endpoint originating from non-administrative accounts

Detection Strategies

Review Indico and reverse proxy access logs for authenticated calls to the deprecated user details API path
Correlate account activity against role assignments to identify non-admin users invoking admin-oriented endpoints
Enable audit logging on Flask-Multipass authentication backends to track API consumers

Monitoring Recommendations

Alert on high-cardinality user ID lookups from a single account within short time windows
Track HTTP 200 responses on the legacy endpoint by role and flag non-admin callers
Forward web server and application logs to a centralized analytics platform for retrospective review

How to Mitigate CVE-2025-59034

Immediate Actions Required

Upgrade Indico to version 3.3.8 or later, which contains the access control fix
Audit access logs for the legacy user details API to identify prior enumeration activity
Rotate credentials or notify users if unauthorized profile access is confirmed

Patch Information

The fix is included in Indico Release v3.3.8. The maintainers strengthened the access check on the legacy user details endpoint so that only administrators or the profile owner receive data. Full remediation details are published in the GitHub Security Advisory GHSA-4269-mcfh-cp7q.

Workarounds

Restrict access to the affected legacy API at the web server or reverse proxy layer using path-based access rules
Limit endpoint access to administrator source IP ranges until the upgrade is applied
Disable or block the legacy API route entirely if it is not required by integrations

bash

# Example nginx restriction for the legacy user details API
location ~ ^/api/user/ {
    allow 10.0.0.0/8;      # internal admin network
    deny all;
    proxy_pass http://indico_backend;
}