# CVE-2026-53538: python-multipart: Python-Multipart is a streaming multipart parser for Python

CVE-2026-53538 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-53538, released June 22, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-53538
- Priority: Routine
- CVSS: 3.7 (low)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 22, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-multipart Debian 14 | 0.0.32-1 | [DEBIAN-CVE-2026-53538](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53538.md) | Jun 22, 2026 |
| Linux | python-python-multipart opensuse-leap 16.0 | 0.0.20-160000.5.1 | [OPENSUSE-SU-2026:21066-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21066-1.md) | Jun 26, 2026 |
| Linux | python-python-multipart sles 16.0 | 0.0.20-160000.5.1 | [SUSE-SU-2026:22372-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22372-1.md) | Jun 26, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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