CVE-2026-44556: Open WebUI access control bypass in OpenAI /responses endpoint

Summary

Open WebUI versions prior to 0.9.0 expose the /responses endpoint in the OpenAI router, which accepts any authenticated user. The endpoint forwards requests straight to upstream LLM providers without the model ownership, group membership and AccessGrants checks that generate_chat_completion enforces. Any authenticated user can therefore use any configured model by POSTing an arbitrary model ID to /api/openai/responses.

Mitigation

Fixed in 0.9.0.

Affected packages in the Exposure Registry

Matched by package name and ecosystem. Each entry shows whether the package delegates to a language model and how many tracked packages depend on it.

• open-webuiPyPILLM dependency since 2024-05-20

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