CVE-2026-56398 open webui vulnerability
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.
Quick answer
openwebui open webui should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Review vendor advisory for affected versions.
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-56398 affects openwebui open webui and is rated high. 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. Fix this first on internet-facing or admin systems. The practical fix is to upgrade Open WebUI to 0.9.5 or a later patched release and block unsafe SVG profile images, then verify the system is no longer exposed.
- Inventory every server, container, appliance, cluster, plugin, or device that uses openwebui open webui.
- Check the installed version and configuration against CVE-2026-56398 and the linked advisory.
- Apply the vendor fix: upgrade Open WebUI to 0.9.5 or a later patched release and block unsafe SVG profile images.
- Keep the Open WebUI admin area private and limit trusted origins, uploads, and function endpoints.
- Disable or isolate the affected feature if you cannot update right away.
- Review admin sessions, function changes, profile image changes, and token use for suspicious activity.
- Rotate secrets, rebuild affected systems, or reset sessions if you suspect compromise.
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Verify the fix
- Confirm openwebui open webui is running the patched version or the approved mitigation is active.
- Confirm affected public, admin, API, tunnel, or cluster access is limited to trusted users.
- Repeat the risky workflow or a safe test case and confirm the issue no longer appears.
- Review logs again after the fix for crashes, bypass attempts, file access, or suspicious changes.
- Save version, config, log, and scan evidence for your remediation record.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-56398?
openwebui open webui should be checked against the vendor advisory and trusted references linked on this page.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.