Availability degradation via negative length unbounded read

Resource exhaustion in Kludex python-multipart before 0.0.31 allows remote attackers to degrade availability via a negative Content-Length header. parse_form converts the header to an integer without rejecting negative values, so its remaining-length calculation passes -1 to input_stream.read() and reads the complete stream at once. Exposure requires bespoke WSGI or http.server code that forwards an attacker-controlled header directly to parse_form; concurrent requests can raise memory use and degrade service without a reported complete outage.