# CVE-2026-53537: python-multipart: Python-Multipart is a streaming multipart parser for Python

CVE-2026-53537 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-53537, released June 22, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-53537
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0029
- 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, 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-multipart Debian 14 | 0.0.32-1 | [DEBIAN-CVE-2026-53537](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53537.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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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