CVE-2026-42561 HIGH

CVE-2026-42561: Python-Multipart: Denial of Service via unbounded multipart part headers

Vendor Kludex
Product python-multipart
Weakness CWE-770 · Uncontrolled resource consumption
Published May 13, 2026
Last update May 14, 2026

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

What the vulnerability does

Description

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.27, python-multipart has a denial of service vulnerability in multipart part header parsing. When parsing multipart/form-data, MultipartParser previously had no limit on the number of part headers or the size of an individual part header. An attacker could send a request with either many repeated headers without terminating the header block or a single very large header value, causing excessive CPU work before request rejection or completion. This vulnerability is fixed in 0.0.27.

Key dates

Disclosure timeline

May 13, 2026 CVE published
May 14, 2026 Record updated