Open WebUI permitted any authenticated user to retrieve and alter private knowledge bases through its retrieval APIs. The vulnerability, an IDOR flaw, bypassed the platform’s collection‑level access controls by using raw UUIDs that were not checked by the validation routine. As a result, an attacker could read, inject, or overwrite another user’s private data, compromising both confidentiality and integrity of the knowledge bases. The flaw stems from improper validation of collection names and is documented as CWE‑639.

The issue affects all instances of the Open WebUI platform running versions prior to 0.9.5. Users who have not upgraded to v0.9.5 or later are at risk, regardless of other configuration settings. The product is branded as open-webui:open-webui; no specific sub‑products are listed.

The CVSS score of 7.5 indicates a high severity. Exploitation requires valid credentials and knowledge of a target UUID, so the attack vector is an authenticated user. While the EPSS score is currently unavailable, the high CVSS and known confirmation of IDOR in public advisories suggest a non‑negligible risk. This vulnerability is not listed in the CISA KEV catalog, but the potential for internal data leakage warrants immediate action.