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

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

https://cvefeed.io/rssfeed/latest.atom / Mon, 06/22/2026 - 22:01
CVE ID :CVE-2026-53537
Published : June 22, 2026, 4:57 p.m. | 2 hours, 43 minutes ago
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. This vulnerability is fixed in 0.0.30.
Severity: 0.0 | NA
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