{"schemaVersion":3,"id":"CVE-2026-53537","aliases":["GHSA-vffw-93wf-4j4q","PYSEC-2026-3041","UBUNTU-CVE-2026-53537","DEBIAN-CVE-2026-53537","CGA-gh2g-q2c6-4fg5","CGA-wwwg-6cg7-9j3m","CGA-2v99-qxr8-wpr6","CGA-2v9f-rvhj-26g4","CGA-5p57-6735-93rq","CGA-8gj2-m98w-mf9c","CGA-92qg-2x86-j49x","CGA-9fpq-vx8j-5v3w","CGA-f7mj-c7xx-2gvx","CGA-p2qw-w669-v45h","CGA-pp74-m8m7-px66","CGA-qcjr-pcw5-fg4h","CGA-qmm4-5wh6-fw59","CGA-rhrr-r6pm-qfh9","CGA-v85c-g7wm-rhwv","CGA-w56r-pfmm-pmgv","CGA-wvg3-3r94-9vh9"],"status":"published","duplicateOf":null,"title":null,"description":"Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, parse_options_header 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 filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data. Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend. 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