The vulnerability permits unauthenticated network clients to send any Solr streaming expression to the REST endpoint POST /api/v1/index/stream, which then forwards the expression directly to the Solr backend without any access control. The attacker can therefore read the entire Solr index and, for default Solr deployments, modify or delete indexed records. This grants a breach of confidentiality, integrity, and potentially availability of the digitised material repository, classification as CWE‑306.

The issue is present in Intranda Goobi Viewer core versions starting from 4.8.0 up through any build before 26.04.1. Systems running the impacted versions with an unprotected Solr instance expose all indexed content to unauthenticated users. Default Solr setups are especially vulnerable because they lack authentication or fine‑grained access controls.

The CVSS score of 9.8 classifies this as a critical vulnerability. No EPSS score is published, but the lack of authentication and the direct forwarding of arbitrary expressions make exploitation straightforward for anyone with network access to the application. The vulnerability is not yet listed in the CISA KEV catalog, though the exploitation probability is effectively high once the affected application and Solr are publicly reachable.