{"id":"CVE-2026-44556","aliases":["GHSA-hp5m-24vp-vq2q","PYSEC-2026-2734"],"url":"https://o3.security/vulnerability/CVE-2026-44556","summary":"Open WebUI: responses passthrough endpoint lacks access control authorization","details":"## Summary\n\nThe /responses endpoint in the OpenAI router accepts any authenticated user and forwards requests directly to upstream LLM providers without enforcing per-model access control. While the primary chat completion endpoint (generate_chat_completion) checks model ownership, group membership, and AccessGrants before allowing a request, the /responses proxy only validates that the user has a valid session via get_verified_user.\n\nThis allows any authenticated user — regardless of role or group assignment — to interact with any model configured on the instance by sending a POST request to /api/openai/responses with an arbitrary model ID.\n\n## Impact\n\nAs per OWASP TOP 10 LLM:\n\n- **Model Denial of Service (OWASP LLM04):** An unauthorized user can submit resource-intensive requests to expensive models (e.g., o1-pro, GPT-4o) that were explicitly restricted by the administrator. In shared deployments, this can exhaust API budgets or rate limits, causing total service disruption for all legitimate users.\n\n- **Model Theft (OWASP LLM10):** If the instance proxies access to fine-tuned or self-hosted models, unauthorized users can freely interact with them, enabling capability extraction or model distillation without authorization.\n\n- **Access Policy Bypass:** Administrators lose the ability to enforce cost-tier restrictions, team-based model assignments, or compliance boundaries through the existing access control system.\n\nThe endpoint is a raw passthrough proxy and does not resolve workspace model configurations (system prompts, knowledge bases, RAG pipelines). Therefore, workspace-specific confidential data is not directly exposed through this vector.\n\nPR: https://github.com/open-webui/open-webui/pull/23481","published":"2026-05-15T19:46:17.750Z","modified":"2026-08-12T03:51:33.992737956Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H"},"epss":{"score":0.00306,"percentile":0.22682,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"open-webui","fixedVersion":"0.9.0"}],"fix":{"url":"https://github.com/open-webui/open-webui/pull/23481","label":"open-webui/open-webui#23481"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44556.json"},{"type":"ADVISORY","url":"https://github.com/open-webui/open-webui/security/advisories/GHSA-hp5m-24vp-vq2q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44556"},{"type":"WEB","url":"https://github.com/open-webui/open-webui/pull/23481"},{"type":"PACKAGE","url":"https://github.com/open-webui/open-webui"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:33.992737956Z"}}