CVE-2026-42561
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Moderate risk: more likely to be exploited than 57% of all known CVEs.
References
Related Vulnerabilities
Other CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-50387 | High | 7.5 | 100% | - | Fix |
| CVE-2019-11478 | Medium | 5.3 | 95% | - | Fix |
| CVE-2019-11479 | High | 7.5 | 92% | - | Fix |
| CVE-2024-27316 | High | 7.5 | 91% | - | Fix |
| CVE-2022-30522 | High | 7.5 | 90% | - | Fix |
| CVE-2019-9515 | High | 7.5 | 87% | - | Fix |
Common questions
How do I fix CVE-2026-42561?
Upgrade python-multipart on debian unstable to 0.0.32-1 or later.
Is CVE-2026-42561 being actively exploited?
Not that we know of. CVE-2026-42561 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.85% is the estimated probability that it will be exploited in the next 30 days. That is higher than 57% of all scored CVEs.
How severe is CVE-2026-42561?
CVE-2026-42561 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-42561 affect?
Published advisories record a fix for python-multipart (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-07.