high CVSS 7.2

CVE-2026-45395·Python vulnerability

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.5, the tool update endpoint (POST /api/v1/tools/id/{id}/update) is missing the workspace.tools permission check that is present on the tool create endpoint. This allows a user who has been explicitly denied tool management capabilities ( and who the administrator considers untrusted for code execution ) to replace a tool's server-side Python content and trigger execution, bypassing the intended workspace.tools security boundary. This vulnerability is fixed in 0.9.5.

Severity
high
Software
Python
Fixed in
0.9.5
Published
2026-05-15

Affected versions

Until: 0.9.5

Fixed in: 0.9.5

How to fix this CVE

Update Open WebUI to version 0.9.5 or later to address a critical authorization bypass in the tool update endpoint. This vulnerability allows users without proper permissions to modify tool configurations and execute arbitrary Python code on the server. Apply the fix immediately if you are running Open WebUI with multi-user workspace configurations where permission boundaries are enforced.

sudo dnf update python3

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /api/v1/tools/id/.*/update with non-admin Authorization header returning 200 OK instead of 403 Forbidden; tool Python code modifications from unprivileged user accounts; execution of server-side Python code originating from tool configurations modified by non-admin users

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block POST requests to /api/v1/tools/id/*/update endpoints unless the request includes an Authorization header with admin-level credentials. Implement request filtering that validates workspace.tools permission claims before allowing tool update operations. Log all attempts to modify tools and alert on requests from non-privileged accounts.

How to check if you are affected

  1. Step 1: Check the Open WebUI version installed: curl http://localhost:8080/api/version or check the application settings page for the running version number
  2. Step 2: Verify workspace.tools permission enforcement by checking if non-admin users can access POST /api/v1/tools/id/{id}/update endpoint: curl -X POST http://localhost:8080/api/v1/tools/id/test/update -H 'Authorization: Bearer {user_token}' -d '{}' and observe if 403 Forbidden is returned
  3. Step 3: Search application logs for unauthorized tool update attempts: grep -r 'POST /api/v1/tools.*update' /var/log/open-webui/ or application audit logs for 'permission denied' errors on tool endpoints
  4. Step 4: Confirm the fix by checking the Open WebUI version is 0.9.5 or higher: curl http://localhost:8080/api/version | grep -E '0\.(9\.[5-9]|[1-9][0-9])' and verify that unprivileged users receive proper authorization errors when attempting tool modifications

FAQ

What is CVE-2026-45395?

This is an authorization bypass vulnerability in Open WebUI's tool update endpoint that fails to enforce the workspace.tools permission check. An attacker with a user account but without tool management privileges can bypass security controls to modify tool definitions and execute arbitrary Python code on the server.

Is CVE-2026-45395 being actively exploited?

No, this vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, the authorization bypass nature makes it a high-priority fix for deployments with untrusted users.

What versions of Open WebUI are affected by CVE-2026-45395?

All versions of Open WebUI prior to 0.9.5 are vulnerable. The vulnerability was introduced in earlier versions and patched in version 0.9.5 and later.

How do I check if my server is vulnerable to CVE-2026-45395?

Run 'curl http://localhost:8080/api/version' to get your Open WebUI version. If it is below 0.9.5, your installation is vulnerable. Additionally, test authorization by attempting a POST request to the tool update endpoint with a non-admin user token and verify that a 403 Forbidden response is returned.

Does Defensia detect CVE-2026-45395?

Yes — Defensia's CVE advisory scanner compares installed Open WebUI versions against the NVD database. If Open WebUI is deployed on a monitored server, CVE-2026-45395 will appear in your dashboard with remediation steps and version comparison details.

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References

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