CVE-2026-53537

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.

CVSS v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*

History

26 Jun 2026, 19:54

Type	Values Removed	Values Added
References	~~() https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q -~~	() https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q - Vendor Advisory
First Time		Fastapiexpert python-multipart Fastapiexpert
CPE		cpe:2.3:a:fastapiexpert:python-multipart::::::python::*

22 Jun 2026, 18:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-22 18:16

Updated : 2026-06-26 19:54

NVD link : CVE-2026-53537

Mitre link : CVE-2026-53537

CVE.ORG link : CVE-2026-53537

JSON object : View

Products Affected

fastapiexpert

python-multipart

CWE

CWE-20

Improper Input Validation

CWE-436

Interpretation Conflict

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