Kludex python-multipart up to 0.0.29 on Python interpretation conflict

Summaryinfo

A vulnerability identified as problematic has been detected in Kludex python-multipart up to 0.0.29 on Python. Affected is an unknown function. This manipulation causes interpretation conflict. This vulnerability is registered as CVE-2026-53538. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Kludex python-multipart up to 0.0.29 on Python. Affected by this vulnerability is some unknown functionality. The manipulation with an unknown input leads to a interpretation conflict vulnerability. The CWE definition for the vulnerability is CWE-436. Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state. As an impact it is known to affect integrity. The summary by CVE is:

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-53538 since 06/09/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available.

Upgrading to version 0.0.30 eliminates this vulnerability.

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Productinfo

Type

• Programming Language Software

Vendor

• Kludex

Name

• python-multipart

Version

• 0.0.1
• 0.0.2
• 0.0.3
• 0.0.4
• 0.0.5
• 0.0.6
• 0.0.7
• 0.0.8
• 0.0.9
• 0.0.10
• 0.0.11
• 0.0.12
• 0.0.13
• 0.0.14
• 0.0.15
• 0.0.16
• 0.0.17
• 0.0.18
• 0.0.19
• 0.0.20
• 0.0.21
• 0.0.22
• 0.0.23
• 0.0.24
• 0.0.25
• 0.0.26
• 0.0.27
• 0.0.28
• 0.0.29

Website

• Product: https://github.com/Kludex/python-multipart/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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