Vulnerability Report

CVE-2026-40347

Title: DoS in multipart parser

DoS

Proof Of Concept

No public PoC currently indexed for CVE-2026-40347.

CWE Category CWE-400
Published Date Apr 18, 2026
Modified Date Apr 24, 2026
Exploit Status Not Found
Score 5.3 CVSS v3.1
Exploit Probability (EPSS)
0.35%

Vulnerability Summary

CVE-2026-40347: 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.

Impacted Vendors

F
fastapiexpert 1

Reference Links

https://github.com/Kludex/python-multipart/releases/tag/0.0.26 https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pj
CVSS v3.1
Source Entity [email protected]
Severity MEDIUM
5.3
Attack Vector
NETWORK
Complexity
LOW
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-40347 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity LOW
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected Stack

No specific products linked.