Skip to content
Fencer Vulns
high 7.5

CVE-2026-28356 json

ReDoS in multipart 1.3.0 - `parse_options_header()`

published 2026-03-12 7 mo ago modified 2026-09-10 1 mo ago also GHSA-p2m9-wcp5-6qw3 , PYSEC-2026-2670 , EUVD-2026-11607

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 58%
public exploits
0
none known

Summary

multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.

Patch / fix

  • pypi multipart 1.2.2, 1.3.1
  • Red Hat Red Hat AI Inference Server 3.2 1774351144, 1774547384, 1775252598
  • Red Hat Red Hat OpenShift AI 2.25 1776247907, 1776338381, 1782397826, 1783998774, 1783998857
  • Red Hat Red Hat OpenShift AI 3.3 1782996080
  • multipart Debian 13 1.2.1-2+deb13u1
  • multipart Debian 14 1.3.1-1

debian advisories DEBIAN-CVE-2026-28356

  • multipart Ubuntu 25.10 1.2.1-2+deb13u1build0.25.10.1
  • multipart Ubuntu 26.04 LTS 1.3.0-3ubuntu0.1

ubuntu advisories UBUNTU-CVE-2026-28356

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-multipart openSUSE Tumbleweed 1.3.1-1.1

opensuse advisories openSUSE-SU-2026:10333-1

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-2026-28356 updated cvss 7.5

multipart: denial of service via maliciously crafted HTTP or multipart segment headers

  • Red Hat Lightspeed Core lightspeed-core/rag-tool-rhel9, lightspeed-core/lightspeed-stack-rhel9
    affected: workaround, no fix available “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-service-api-rhel9
    affected: workaround, no fix planned “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat AI Inference Server rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaiis/vllm-spyre-rhel9, rhaiis/vllm-neuron-rhel9, rhaiis-preview/vllm-cuda-rhel9
    affected: workaround, no fix available, no fix planned “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • 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 Red Hat Satellite 6 satellite/iop-vmaas-rhel9, satellite/iop-advisor-engine-rhel9, satellite/iop-host-inventory-rhel9, satellite/iop-vulnerability-engine-rhel9
    affected: workaround, no fix available “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat AI Inference Server 3.2 rhaiis 1774351144, rhaiis 1774547384, rhaiis 1775252598
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2026:6761
  • Red Hat OpenShift AI 2.25 rhoai 1776247907, rhoai 1776338381, rhoai/odh-vllm-cpu-rhel9 1782397826, rhoai/odh-vllm-cuda-rhel9 1783998774, rhoai/odh-vllm-rocm-rhel9 1783998857
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2026:10184
  • Red Hat OpenShift AI 3.3 rhoai/odh-vllm-cpu-rhel9 1782996080, rhoai/odh-vllm-cpu-rhel9 1790274961
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2026:73987
  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9
    not affected: component not present
show 4 more
  • 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
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-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, +22 more
    not affected: component not present
  • Red Hat OpenShift AI 2.25 rhoai 1775144403, rhoai 1776243157, rhoai 1776243163, rhoai 1776243192, rhoai 1776243217, rhoai 1776243229, +142 more Red Hat OpenShift AI 3.3 rhoai/odh-cli-rhel9 1782471642, rhoai/odh-cli-rhel9 1790070206, rhoai/rhai-cli-rhel9 1782471642, rhoai/rhai-cli-rhel9 1790070206, rhoai/odh-mlflow-rhel9 1782917849, rhoai/odh-mlflow-rhel9 1789653606, +158 more
    not affected: vulnerable code not present
  • Red Hat Satellite 6 satellite/foreman-mcp-server-rhel9
    not affected: component 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
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.84% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi multipart
>=1.3.0, <1.3.1
<1.2.2
1.3.1
1.2.2

Affected products

  • defnull multipart
  • Red Hat Red Hat AI Inference Server 3.2
  • Red Hat Red Hat OpenShift AI 2.25
  • Red Hat Red Hat OpenShift AI 3.3
  • Red Hat Lightspeed Core
  • Red Hat OpenShift Lightspeed
  • Red Hat Red Hat AI Inference Server
  • Red Hat Red Hat Ansible Automation Platform 2
  • Red Hat Red Hat Enterprise Linux AI (RHEL AI) 3
  • Red Hat Red Hat OpenShift AI (RHOAI)
  • Red Hat Red Hat Satellite 6

Classification

Weakness
  • CWE-1333 Inefficient Regular Expression Complexity

References

Sources

Fencer Vulns 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.