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

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
Kludex / python-multipart	affected < 0.0.27

CWE

CWE-770

References

https://github.com/Kludex/python-multipart/security/advisories/GHSA-pp6c-gr5w-3c5g

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in python-multipart. A remote attacker can exploit this denial of service (DoS) vulnerability by sending a specially crafted request with an excessive number of part headers or a single very large header value during multipart/form-data parsing. This can lead to excessive CPU utilization, resulting in a denial of service for the affected system.