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Fencer Intel
medium 5.3

CVE-2026-40347 json

Python-Multipart affected by Denial of Service via large multipart preamble or epilogue data

published 6mo ago modified 14d ago also EUVD-2026-23615 , GHSA-mj87-hwqh-73pj , PYSEC-2026-3038

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi python-multipart 0.0.26
  • fastapiexpert python-multipart 0.0.26
  • kludex python-multipart 0.0.26
  • kludex python_multipart 0.0.26
  • python-multipart Debian 14 0.0.26-1

debian advisories DEBIAN-CVE-2026-40347

  • python-python-multipart SLES for SAP applications 16.0, SLES 16.0 0.0.20-160000.4.1

suse advisories SUSE-SU-2026:21999-1

  • python-python-multipart openSUSE Tumbleweed 0.0.26-1.1

opensuse advisories openSUSE-SU-2026:10597-1

Is CVE-2026-40347 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-40347 updated cvss 5.9

python-multipart: Python-Multipart: Denial of Service via crafted multipart/form-data requests

  • Red Hat Lightspeed Core lightspeed-core/rag-tool-rhel9, lightspeed-core/lightspeed-stack-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9, openshift-lightspeed/lightspeed-service-api-rhel9 Red Hat AI Inference Server rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaiis/vllm-cuda-rhel9, rhaiis/vllm-rocm-rhel9, rhaiis/vllm-spyre-rhel9, rhaiis/vllm-neuron-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/mcp-tools-rhel9, ansible-automation-platform-25/lightspeed-chatbot-rhel8, ansible-automation-platform-26/lightspeed-chatbot-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/disk-image-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more
    +2 more products
    Red Hat OpenShift AI (RHOAI) rhoai/odh-mlserver-rhel9, rhoai/odh-vllm-cuda-rhel9, rhoai/odh-vllm-rocm-rhel9, rhoai/odh-caikit-nlp-rhel9, rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-kserve-agent-rhel9, +7 more Red Hat Satellite 6 satellite/iop-vmaas-rhel9, satellite/foreman-mcp-server-rhel9, satellite/iop-advisor-engine-rhel9, satellite/iop-host-inventory-rhel9, satellite/iop-vulnerability-engine-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi python-multipart
<0.0.26
0.0.26

Affected products

  • Kludex python-multipart

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-834 Excessive Iteration

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.