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.
History

Fri, 15 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Open-webui
Open-webui open-webui
Vendors & Products Open-webui
Open-webui open-webui

Fri, 15 May 2026 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 15 May 2026 20:15:00 +0000

Type Values Removed Values Added
Description 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.
Title Open WebUI: Base Model Routing Bypasses Access Control via Model Chaining
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 7.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-05-15T19:48:35.352Z

Updated: 2026-05-15T20:21:22.063Z

Reserved: 2026-05-06T20:59:00.594Z

Link: CVE-2026-44555

cve-icon Vulnrichment

Updated: 2026-05-15T20:21:17.218Z

cve-icon NVD

Status : Received

Published: 2026-05-15T20:16:46.967

Modified: 2026-05-15T21:16:35.913

Link: CVE-2026-44555

cve-icon Redhat

No data.