CVE-2026-56398: Open WebUI - Stored Cross-Site Scripting via OAuth Picture Claim SVG Data URI
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Open WebUIto a version that resolves this vulnerability.Fixed in 0.9.5 - Configuration
Modify the OAuth picture claim flow so the picture claim URL MIME type is inferred from the HTTP Content-Type header rather than the file extension, preventing SVG files from bypassing the profile image validator and being stored as data URIs.
Open WebUI (OAuth picture claim handling) MIME type inference source = Infer from the Content-Type header (not file extension)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-56398?
The severity of CVE-2026-56398 is high with a score of 8.5.
How do I fix CVE-2026-56398?
To fix CVE-2026-56398, upgrade to Open WebUI version 0.9.5 or later.
What types of attacks could exploit CVE-2026-56398?
CVE-2026-56398 can be exploited for stored cross-site scripting (XSS) attacks through malicious SVG data URIs.
What software is affected by CVE-2026-56398?
CVE-2026-56398 affects Open WebUI versions before 0.9.5.
How does CVE-2026-56398 occur?
CVE-2026-56398 occurs because the picture claim URL MIME type is derived from the file extension, allowing SVG files to bypass validation.