CVE-2026-53537
Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters
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.
INFO
Published Date :
June 22, 2026, 4:57 p.m.
Last Modified :
June 22, 2026, 4:57 p.m.
Remotely Exploit :
No
Source :
GitHub_M
Affected Products
The following products are affected by CVE-2026-53537
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update Python-Multipart to version 0.0.30.
- Ensure upstream components handle headers consistently.
- Validate Content-Disposition headers for compliance.
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