CVE-2026-53537 Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, parseoptionsheader parsed Content-Disposition and Content-Type headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax filename=charset'lang'value, name=...,...