Onyx MCP API Vulnerability Exposes Users' OAuth Authorization Headers

Onyx, an open-source AI platform, is affected by an OAuth Authorization header exposure vulnerability in its MCP server API endpoints. The GET /api/mcp/servers and GET /api/mcp/servers/persona/{persona_id} endpoints can expose another user's OAuth Authorization header.

The flaw occurs because OnyxTokenStorage.set_tokens and OnyxTokenStorage.set_client_info in backend/onyx/server/features/mcp/api.py copy per-user tokens into a shared admin MCPConnectionConfig row. _db_mcp_server_to_api_mcp_server then returns that row through auth_template.headers to any BASIC_ACCESS user.

• Affected versions: prior to 3.1.10, 3.2.14, and 4.0.0
• Fixed versions: 3.1.10, 3.2.14, and 4.0.0