GeoServer is an open source server that allows users to share and edit geospatial data. An improper URI validation vulnerability exists that enables an unauthorized attacker to perform XML External Entities (XEE) attack, then send GET request to any HTTP server. By default, GeoServer use PreventLocalEntityResolver class from GeoTools to filter out malicious URIs in XML entities before resolving them. The URI must match the regex (?i)(jar:file|http|vfs)[^?#;]*\\.xsd. But the regex leaves a chance for attackers to request to any HTTP server or limited file. Attacker can abuse this to scan internal networks and gain information about them then exploit further. GeoServer 2.25.0 and greater default to the use of ENTITY_RESOLUTION_ALLOWLIST and does not require you to provide a system property.

Affected: Maven: org.geoserver.web:gs-web-app, Maven: org.geoserver.main:gs-main

### Summary An improper URI validation vulnerability exists that enables an unauthorized attacker to perform XML External Entities (XEE) attack, then send GET request to any HTTP server. Attacker can abuse this to scan internal networks and gain information about them then exploit further. Moreover, attacker can read limited `.xsd` file on system.

### Details By default, GeoServer use `PreventLocalEntityResolver` class from GeoTools to filter out malicious URIs in XML entities before resolving them. The URI must match the regex `(?i)(jar:file|http|vfs)[^?#;]*\\.xsd`. But the regex leaves a chance for attackers to request to any HTTP server or limited file.

### Impact

An unauthenticated attacker can: 1. Scan internal network to gain insight about it and exploit further. 2. SSRF to endpoint ends with `.xsd`. 3. Read limited `.xsd` file on system.

### Mitigation

1. Define the system property ``ENTITY_RESOLUTION_ALLOWLIST`` to limit the supported external schema locaitons. 2. The built-in allow list covers the locations required for the operation of OGC web services: ``www.w3.org``,``schemas.opengis.net``,``www.opengis.net``,``inspire.ec.europa.eu/schemas``. 3. The [user guide](https://docs.geoserver.org/latest/en/user/production/config.html#production-config-external-entities) provides details on how to add additional locations (this is required for app-schema plugin where a schema is supplied to define an output format).

### Resolution

1. GeoServer 2.25.0 and greater d…

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in GeoServer ausnutzen, um Informationen offenzulegen oder Sicherheitsvorkehrungen zu umgehen.