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.
Metrics
Affected Vendors & Products
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| Kludex |
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OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.
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| Kludex |
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References
History
Mon, 22 Jun 2026 20:15:00 +0000
| Type | Values Removed | Values Added |
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| First Time appeared |
Kludex
Kludex python-multipart |
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| Vendors & Products |
Kludex
Kludex python-multipart |
Mon, 22 Jun 2026 17:30:00 +0000
| Type | Values Removed | Values Added |
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| 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. | |
| Title | Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters | |
| Weaknesses | CWE-20 CWE-436 |
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| References |
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| Metrics |
cvssV3_1
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MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-06-22T16:57:21.496Z
Reserved: 2026-06-09T18:13:07.262Z
Link: CVE-2026-53537
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
Updated: 2026-06-22T20:00:05Z