ChatterBot is a machine learning, conversational dialog engine for creating chat bots. ChatterBot versions up to 1.2.10 are vulnerable to a denial-of-service condition caused by improper database session and connection pool management. Concurrent invocations of the get_response() method can exhaust the underlying SQLAlchemy connection pool, resulting in persistent service unavailability and requiring a manual restart to recover. Version 1.2.11 fixes the issue.