{"id":"PYSEC-2026-2718","summary":"Open WebUI: Authenticated users can target arbitrary configured Ollama backends via unguarded url_idx path parameter","details":"## Summary\n\nSeveral direct, index-addressed Ollama proxy routes accept a caller-supplied `url_idx`\npath parameter and use it as a raw index into the admin-configured `OLLAMA_BASE_URLS`\nlist. Access control on these routes validates only whether the user may use the\nrequested *model*, never which *backend* the request is routed to. Any authenticated\nuser can append an arbitrary `url_idx` to force their request onto an Ollama backend\nthey were never authorized to reach, including internal, higher-privilege, or\nexplicitly admin-disabled backends.\n\n## Affected endpoints\n\nAll indexed Ollama routes that resolve the backend through `get_ollama_url()`:\n\n```\nPOST /ollama/api/chat/{url_idx}\nPOST /ollama/api/generate/{url_idx}\nPOST /ollama/api/embed/{url_idx}\nPOST /ollama/api/embeddings/{url_idx}\nPOST /ollama/v1/chat/completions/{url_idx}\nPOST /ollama/v1/completions/{url_idx}\nPOST /ollama/v1/messages/{url_idx}\nPOST /ollama/v1/responses/{url_idx}\n```\n\n## Root cause\n\n`backend/open_webui/routers/ollama.py` — `get_ollama_url()` consults the\nmodel-to-backend allow-list (`OLLAMA_MODELS[model][\"urls\"]`) only when `url_idx` is\nomitted. When the caller supplies `url_idx`, that mapping is skipped and the value is\nused directly as an index:\n\n```python\nasync def get_ollama_url(request: Request, model: str, url_idx: Optional[int] = None):\n    if url_idx is None:\n        models = request.app.state.OLLAMA_MODELS\n        if model not in models:\n            raise HTTPException(...)\n        url_idx = random.choice(models[model].get(\"urls\", []))\n    url = request.app.state.config.OLLAMA_BASE_URLS[url_idx]   # caller-controlled, no authz\n    return url, url_idx\n```\n\nThe outbound request is then sent to that backend using the backend's own configured\nAPI key. Backends an admin has disabled (`OLLAMA_API_CONFIGS[\"\u003cidx\u003e\"].enable = false`)\nare hidden from model discovery but remain reachable through the indexed route, because\nthe disabled state is never re-checked at request time.\n\n## Impact\n\nA verified, non-admin user with read access to any single model can:\n- route requests to internal / higher-capability / restricted Ollama backends in\n  multi-backend deployments, bypassing backend-level isolation;\n- reach backends the admin has explicitly disabled;\n- have those requests authenticated with the target backend's configured API key\n  (the key is used server-side; it is not returned to the attacker);\n- consume the restricted backend's compute.\n\nThere is no cross-user data disclosure and no exfiltration of the backend credential\nitself; the impact is unauthorized access to, and use of, restricted backend resources.\n\n## Affected / Patched\n\n- Affected: `\u003c= 0.9.5`\n- Patched: `\u003e= 0.9.6`\n\n## Fix\n\n0.9.6 adds `validate_ollama_backend_idx()`, invoked on every indexed route (directly and\nvia `get_ollama_url()`), which returns 403 for any non-admin caller-supplied `url_idx`\nthat is not in the requested model's allowed `urls`. Because disabled backends are absent\nfrom every model's `urls`, the same check also blocks routing to disabled backends.","aliases":["CVE-2026-54021","GHSA-9rpj-v7hf-vv2w"],"modified":"2026-07-13T16:32:18.829322998Z","published":"2026-07-13T15:46:19.930457Z","references":[{"type":"WEB","url":"https://github.com/open-webui/open-webui/security/advisories/GHSA-9rpj-v7hf-vv2w"},{"type":"PACKAGE","url":"https://github.com/open-webui/open-webui"},{"type":"PACKAGE","url":"https://pypi.org/project/open-webui"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-9rpj-v7hf-vv2w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54021"}],"affected":[{"package":{"name":"open-webui","ecosystem":"PyPI","purl":"pkg:pypi/open-webui"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.6"}]}],"versions":["0.1.124","0.1.125","0.2.0","0.2.1","0.2.2","0.2.3","0.2.4","0.2.5","0.3.0","0.3.1","0.3.10","0.3.12","0.3.13","0.3.14","0.3.15","0.3.16","0.3.17","0.3.17.dev2","0.3.17.dev3","0.3.17.dev4","0.3.17.dev5","0.3.18","0.3.19","0.3.2","0.3.20","0.3.21","0.3.22","0.3.23","0.3.24","0.3.25","0.3.26","0.3.27","0.3.27.dev1","0.3.27.dev2","0.3.27.dev3","0.3.28","0.3.29","0.3.3","0.3.30","0.3.30.dev1","0.3.30.dev2","0.3.31","0.3.31.dev1","0.3.32","0.3.33","0.3.33.dev1","0.3.34","0.3.35","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.0.dev1","0.4.0.dev2","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.6.dev1","0.4.7","0.4.8","0.5.0","0.5.0.dev1","0.5.0.dev2","0.5.1","0.5.10","0.5.11","0.5.12","0.5.13","0.5.14","0.5.15","0.5.16","0.5.17","0.5.18","0.5.19","0.5.2","0.5.20","0.5.3","0.5.3.dev1","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9","0.6.0","0.6.1","0.6.10","0.6.11","0.6.12","0.6.13","0.6.14","0.6.15","0.6.16","0.6.18","0.6.19","0.6.2","0.6.20","0.6.21","0.6.22","0.6.23","0.6.24","0.6.25","0.6.26","0.6.26.dev1","0.6.27","0.6.28","0.6.29","0.6.3","0.6.30","0.6.31","0.6.32","0.6.33","0.6.34","0.6.35","0.6.36","0.6.37","0.6.38","0.6.39","0.6.4","0.6.40","0.6.41","0.6.42","0.6.43","0.6.5","0.6.6","0.6.6.dev1","0.6.7","0.6.8","0.6.9","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.10","0.8.11","0.8.12","0.8.2","0.8.3","0.8.4","0.8.5","0.8.6","0.8.7","0.8.8","0.8.9","0.9.0","0.9.1","0.9.2","0.9.3","0.9.4","0.9.5"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/open-webui/PYSEC-2026-2718.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L"}]}