CVE-2026-45339: Openwebui Open Webui

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, Open WebUI allows admins to restrict which API endpoints an API key can access. When an API key is restricted from /api/v1/messages, requests using the Authorization: Bearer sk-... header are correctly blocked with 403. However, the same key sent via the x-api-key header bypasses the restriction entirely — the request is authenticated, the model is invoked, and a full response is returned. This vulnerability is fixed in 0.9.0.

Affected products

• Openwebui Open Webui: before 0.9.0 (fixed in 0.9.0)

Published 2026-05-15. Last modified 2026-06-17.