CVE-2026-56398: Openwebui Open Webui

Critical severity, CVSS 9.0. EPSS: 0.6% chance of exploitation in the next 30 days.

Open WebUI before 0.9.5 contains a stored cross-site scripting vulnerability in the OAuth authentication flow where the picture claim URL MIME type is inferred from file extension rather than Content-Type header, allowing SVG files to bypass the profile image validator and be stored as data URIs. Authenticated users who visit the profile image endpoint receive attacker-controlled SVG content with inline disposition and no default security headers, enabling script execution in the same origin to steal authentication tokens and achieve account takeover.

Affected products

• Openwebui Open Webui: before 0.9.5 (fixed in 0.9.5)

Published 2026-07-15. Last modified 2026-07-16.