CVE-2025-27505 is a medium-severity vulnerability affecting GeoServer, an open-source server platform used for sharing and editing geospatial data. The vulnerability arises from missing authorization checks in the REST API, specifically when accessing REST endpoints with extensions such as 'rest.html'. While the REST API security correctly protects the base REST paths and their subpaths, it fails to secure REST paths that include extensions. This flaw allows an unauthenticated attacker to bypass the default REST API security controls and access the REST API index page. Accessing this index page can disclose information about installed extensions, potentially aiding further targeted attacks or reconnaissance. The vulnerability affects GeoServer versions from 2.25.0 up to but not including 2.25.6, and versions 2.26.0 up to but not including 2.26.3. The issue is classified under CWE-862 (Missing Authorization). The vulnerability does not allow modification or deletion of data but leaks some information about the system configuration. The CVSS v3.1 base score is 5.3 (medium), reflecting network attack vector, low complexity, no privileges required, no user interaction, and limited confidentiality impact. The vendor has fixed the vulnerability in versions 2.25.6 and 2.26.3. As a workaround, administrators can modify the GeoServer security configuration file (config.xml) to extend the REST filter paths to include patterns like /rest.* and /rest/**, and similarly for the gwc filter, then restart GeoServer to enforce proper authorization on these extended paths.

For European organizations using GeoServer to manage and serve geospatial data, this vulnerability poses a moderate risk. GeoServer is often used by government agencies, urban planners, environmental organizations, and utilities to share sensitive geospatial information. Although the vulnerability does not allow direct data modification or deletion, unauthorized access to the REST API index page can reveal information about installed extensions and potentially expose system configuration details. This information leakage can facilitate further reconnaissance and targeted attacks, increasing the risk of subsequent exploitation. In sectors where geospatial data confidentiality is critical—such as defense, critical infrastructure, and urban planning—this could lead to privacy violations or intelligence gathering by malicious actors. Since exploitation requires no authentication or user interaction and can be performed remotely, the attack surface is broad. However, the lack of direct data integrity or availability impact limits the severity. Organizations relying on vulnerable GeoServer versions should consider the potential for indirect impacts, including reputational damage and compliance issues related to data protection regulations like GDPR if sensitive information is exposed.

To mitigate this vulnerability, European organizations should promptly upgrade GeoServer to versions 2.25.6 or 2.26.3 or later, where the issue is fully resolved. If immediate upgrade is not feasible, apply the recommended workaround by editing the ${GEOSERVER_DATA_DIR}/security/config.xml file to modify the REST and GWC filter paths to include patterns such as /rest.* and /rest/**, and /gwc/rest.* and /gwc/rest/** respectively. After making these changes, restart the GeoServer service to apply the new security filters. Additionally, organizations should audit their GeoServer deployments to identify any unauthorized access attempts or unusual activity around the REST API endpoints. Implement network-level access controls to restrict access to GeoServer management interfaces to trusted IP ranges. Monitoring and logging REST API access can help detect exploitation attempts early. Finally, ensure that GeoServer instances are not unnecessarily exposed to the public internet and are protected behind firewalls or VPNs where possible.