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.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Kludex | python-multipart | affected |
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Advisories
| Source | ID | Title |
|---|---|---|
 Github GHSA |
GHSA-vffw-93wf-4j4q | python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters |
Fixes
Solution
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Workaround
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References
History
Mon, 22 Jun 2026 17:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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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Projects
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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
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