CVE-2026-28356 ReDoS in multipart 1.3.0 - `parse_options_header()`

multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parseoptionsheader function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking ReDoS when parsing maliciously crafted HTTP or multipar...