Auth bypass in Open-Webui
CVE-2026-44555
Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, Open WebUI supports model composition via base_model_id: a user-defined model (e.g., "Cheap Assistant") can reference an existing base model (e.g., "gpt-4-turbo-restricted") that provides the actual inference capability. When a user queries the composed model, the access control pipeline verifies the user has access to the composed model but never re-verifies access to the chained base model. Additionally, the model creation and import endpoints accept arbitrary base_model_id values without checking that the caller has access to that base model. Combined, this allows any user with the default model creation permission to create a model that chains to a restricted base model — and then invoke it, causing the server to dispatch the request to the restricted base model using the admin-configured API key. This vulnerability is fixed in 0.9.0.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L.
EPSS exploit prediction
EPSS: 0.003 (25.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Open-Webui — versions < 0.9.0
- Openwebui Open Webui
Weakness classification (CWE)
References
- github.com/open-webui/open-webui/security/advisories/GHSA-9vvh-qmjx-p4q8 (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-44555?
- CVE-2026-44555 is a high-severity vulnerability in Open-Webui, classified under Missing Authorization. CVSS score: 7.6/10. Published 2026-05-15.
- How severe is CVE-2026-44555?
- High severity. CVSS v3 base score is 7.6 out of 10.