{"id":"CVE-2026-44555","summary":"Open WebUI: Base Model Routing Bypasses Access Control via Model Chaining","details":"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.","aliases":["GHSA-9vvh-qmjx-p4q8"],"modified":"2026-07-08T08:13:29.797420554Z","published":"2026-05-15T19:48:35.352Z","database_specific":{"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44555.json","cwe_ids":["CWE-862"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44555.json"},{"type":"ADVISORY","url":"https://github.com/open-webui/open-webui/security/advisories/GHSA-9vvh-qmjx-p4q8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44555"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/open-webui/open-webui","events":[{"introduced":"0"},{"fixed":"f31768e20e5c6b4f6da0ef657877298b359936cf"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.9.0"}],"cpe":"cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*","source":["AFFECTED_FIELD","CPE_RANGE"]}}],"versions":["v0.8.12","v0.8.11","v0.8.10","v0.8.9","v0.8.8","v0.8.7","v0.8.6","v0.8.5","v0.8.4","v0.8.3","v0.8.2","v0.8.1","v0.8.0","v0.7.2","v0.7.1","v0.7.0","v0.6.43","v0.6.42","v0.6.41","v0.6.40","v0.6.39","v0.6.38","v0.6.37","v0.6.36","v0.6.34","v0.6.35","v0.6.33","v0.6.32","v0.6.31","v0.6.30","v0.6.29","v0.6.28","v0.6.27","v0.6.26","v0.6.25","v0.6.24","v0.6.23","v0.6.22","v0.6.21","v0.6.20","v0.6.19","v0.6.18","v0.6.17","v0.6.16","v0.6.15","v0.6.14","v0.6.13","v0.6.12","v0.6.11","v0.6.10","v0.6.9","v0.6.8","v0.6.7","v0.6.6","v0.6.5","v0.6.4","v0.6.3","v0.6.2","v0.6.1","v0.6.0","v0.5.16","v0.5.20","v0.5.19","v0.5.18","v0.5.17","v0.5.15","v0.5.14","v0.5.12","v0.5.13","v0.5.11","v0.5.10","v0.5.9","v0.5.8","v0.5.7","v0.5.6","v0.5.5","v0.5.4","v0.5.3","v0.5.2","v0.5.1","v0.5.0","v0.4.8","v0.4.7","v0.4.6","v0.4.5","v0.4.4","v0.4.3","v0.4.2","v0.4.1","v0.4.0","v0.3.35","v0.3.34","v0.3.33","v0.3.32","v0.3.31","v0.3.30","v0.3.29","v0.3.28","v0.3.27","v0.3.26","v0.3.25","v0.3.24","v0.3.23","v0.3.22","v0.3.21","v0.3.20","v0.3.19","v0.3.18","v0.3.17","v0.3.16","v0.3.15","v0.3.14","v0.3.13","v0.3.12","v0.3.11","v0.3.10","v0.3.9","v0.3.8","v0.3.7","v0.3.6","v0.3.5","v0.3.4","v0.3.3","v0.3.2","v0.3.1","v0.3.0","v0.2.5","v0.2.4","v0.2.3","v0.2.2","v0.2.1","v0.2.0","v0.1.125","v0.1.124","v0.1.123","v0.1.122","v0.1.114","v0.1.121","v0.1.120","v0.1.119","v0.1.118","v0.1.117","v0.1.116","v0.1.115","v0.1.108","v0.1.113","v0.1.112","v0.1.111","v0.1.110","v0.1.109","v0.1.107","v0.1.106","v0.1.105","v0.1.104","v0.1.103","v0.1.102"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44555.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L"}]}