Allocation of Resources Without Limits or Throttling

Summary

The python-multipart is a streaming multipart parser for Python. When parsing form data, python-multipart skips line breaks (CR "\r" or LF "\n") in front of the first boundary and any tailing bytes after the last boundary. This happens one byte at a time and emits a log event each time, which may cause excessive logging for certain inputs. An attacker could abuse this by sending a malicious request with lots of data before the first or after the last boundary, causing a high CPU load and stalling the processing thread for a significant amount of time. In the case of the ASGI application, this could stall the event loop and prevent other requests from being processed, resulting in a Denial of Service (DoS). This issue affects python-multipart versions prior to 0.0.18.