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Vulnerability record · CVE-2026-40347 · published 18 April 2026

CVE-2026-40347: Fastapiexpert python-multipart uncontrolled resource consumption vulnerability

Fastapiexpert · Python Multipart

Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.

5.3 CVSS 3.1 Medium EPSS 0.42% · top 66.4% CWE-400 · Uncontrolled resource consumptionCWE-834 · CWE-834
5.3CVSS 3.1 base score
0.42%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/Kludex/python-multipart/releases/tag/0.0.26 ProductRelease Notes
https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pj Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-40347), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.