Open WebUI’s API endpoint /api/v1/notes/{note_id} does not enforce authorization checks for authenticated users before version 0.8.11. This allows an attacker who has already authenticated, to retrieve notes belonging to other users by guessing or enumerating UUIDs. The result is the unauthorized disclosure of potentially sensitive or private user data, an indirect object reference flaw (CWE‑639).

The vulnerability affects the self‑hosted artificial intelligence platform Open WebUI. Any deployment running a version older than 0.8.11 is susceptible; this includes all releases up to but not including 0.8.11. The vendor is open‑webui and the product is the Open WebUI platform.

The CVSS score of 6.5 indicates moderate severity. The EPSS score is not available, so the current frequency of exploitation is unknown, and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires an authenticated session and the ability to guess or enumerate a note UUID. An attacker could therefore perform a local or remote attack against a logged‑in user, potentially enumerating many notes and revealing private information. Given the lack of known public exploits, the threat is moderate but should be mitigated promptly.