CVE-2026-44556: open-webui Improper Access Control

Vulnerability summary

CVE-2026-44556 is a high (CVSS 7.1) Improper Access Control vulnerability in open-webui. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.7% of scored vulnerabilities.

Timeline

1. 15-05-2026
   PublishedVulnerability first disclosed.
2. 15-05-2026
   Last modifiedVulnerability information updated.

Description

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, the /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. This allows any authenticated user to interact with any model configured on the instance by sending a POST request to /api/openai/responses with an arbitrary model ID. This vulnerability is fixed in 0.9.0.

• CWE-284Improper Access ControlThe product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
• CWE-862Missing AuthorizationThe product does not perform an authorization check when an actor attempts to access a resource or perform an action.