A missing authorization check in Open WebUI before 0.11.4 lets an authenticated user include an explicit backend index on model routes. This bypass allows the server to reach disabled provider backends, causing it to send requests with stored API keys, expose version strings, and enumerate configured connections. The flaw is a classical authorization bypass (CWE‑639) and can lead directly to the disclosure of sensitive credentials and internal configuration details. Additionally, the vulnerability corresponds to CWE‑862 (Missing Authorization) by permitting unauthorized backend calls to be invoked.

The vulnerability affects installations of open‑webui:open‑webui prior to version 0.11.4. Any deployment running a version older than 0.11.4 is susceptible; no additional vendor or version detail is specified.

The CVSS score of 5.3 indicates a medium severity risk, while the EPSS score is approximately 0.275% (less than 1%) and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires that the user already be authenticated to the system; an attacker can then supply a backend index as a path segment or query parameter on listing routes to trigger a request to the disabled provider. The impact is limited to internal information leakage, but the exposure of API keys poses a significant operational risk.