Skip to content
Fencer Intel
low 3.7

CVE-2026-53540 json

Python-Multipart: Negative Content-Length in parse_form buffers the entire body in memory

published 5mo ago modified 17d ago also EUVD-2026-38325 , GHSA-v9pg-7xvm-68hf , PYSEC-2026-3040

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.31, parse_form() did not validate the Content-Length header before using it to bound its chunked read of the request body. A negative Content-Length turned the bounded read into a read-until-EOF, so the entire body was loaded into memory in a single read instead of in fixed-size chunks. This vulnerability is fixed in 0.0.31.

Patch / fix

  • pypi python-multipart 0.0.31
  • fastapiexpert python-multipart 0.0.31
  • kludex python-multipart 0.0.31
  • python-multipart Debian 14 0.0.32-1

debian advisories DEBIAN-CVE-2026-53540

  • python-python-multipart SLES for SAP applications 16.0, SLES 16.0 0.0.20-160000.5.1

suse advisories SUSE-SU-2026:22372-1

  • python-python-multipart openSUSE Leap 16.0 0.0.20-160000.5.1
  • python-python-multipart openSUSE Tumbleweed 0.0.32-1.1

opensuse advisories openSUSE-SU-2026:21066-1openSUSE-SU-2026:11099-1

Is CVE-2026-53540 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-2026-53540 updated cvss 3.7

python-multipart: Python-Multipart: Negative Content-Length in parse_form buffers the entire body in memory

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-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 rhaii/vllm-cpu-rhel9, rhaii/vllm-tpu-rhel9, rhaii/vllm-cuda-rhel9, rhaii/vllm-rocm-rhel9, rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, +7 more Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/mcp-tools-rhel9, ansible-automation-platform-27/mcp-tools-rhel9, ansible-automation-platform-25/lightspeed-chatbot-rhel8, ansible-automation-platform-26/lightspeed-chatbot-rhel9, ansible-automation-platform-27/lightspeed-chatbot-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/disk-image-cuda-rhel9, +2 more
    +3 more products
    Red Hat OpenShift AI (RHOAI) rhoai/odh-automl-rhel9, rhoai/odh-mlserver-rhel9, rhoai/odh-caikit-nlp-rhel9, rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-kserve-agent-rhel9, rhoai/odh-kserve-router-rhel9, +8 more Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9 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 OpenShift Lightspeed openshift-lightspeed/lightspeed-agentic-sandbox-rhel9 Red Hat Hardened Images jaeger
    not affected: vulnerable code not present

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
no
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
OSV 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi python-multipart
<0.0.31
0.0.31

Affected products

  • Kludex python-multipart

Classification

Weakness
  • CWE-1284 Improper Validation of Specified Quantity in Input

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.

The maintainers of Kludex/python-multipart published their own advisory on GitHub. Reviewed sources take precedence over it.

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