PYSEC-2026-3041 python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Summary 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=..., and the filename0/filename1 continuation form is decoded and surfaced...

CVE-2026-53537

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=...,...