A denial-of-service (DoS) vulnerability exists in Action Pack's Action Controller Live streaming feature due to improper handling of the response buffer's end-of-stream marker. When the client stops reading and the response queue is full, pushing the end-of-stream marker blocks and causes threads to wait indefinitely, potentially exhausting server threads. This affects applications using ActionController::Live streaming, including send_stream and Active Storage proxy mode for large files. Fixed versions 8.1.4.1 and 8.0.5.2 address this issue.