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Fencer Intel
high 7.5

CVE-2026-19481 json

@fastify/busboy vulnerable to Denial of Service via prototype-named multipart part header

published 2mo ago modified last mo. also GHSA-x8mw-p69m-v3mx , EUVD-2026-57757

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

@fastify/busboy is a multipart form-data parser. In versions 1.0.0 through 3.2.0, an attacker who can submit multipart form-data can crash the parser by sending a part header whose name is a prototype-inherited property such as __proto__ or constructor. The internal header parser stores headers in a plain JavaScript object and assumes each value is an array, so an inherited property name resolves to a truthy non-array value and triggers a TypeError. In the common pipe integration the failure surfaces as an error event, but in direct write or end usage the exception is thrown synchronously and can terminate the Node.js process, causing an unauthenticated denial of service. The issue is fixed in @fastify/busboy 3.2.1, which creates the header object with a null prototype. Users should upgrade to 3.2.1.

Patch / fix

  • npm @fastify/busboy 3.2.1
  • @fastify/busboy @fastify/busboy 3.2.1

Is CVE-2026-19481 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.

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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-2026-19481 updated cvss 7.5

fastify/busboy: fastify/busboy: Denial of Service from crafted form-data headers

  • Red Hat OpenShift Pipelines openshift-pipelines/pipelines-console-plugin-rhel8
    affected: workaround, no fix available
  • Red Hat Ceph Storage 8 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mib, +17 more Red Hat Ceph Storage 9 ceph, cephadm, librbd1, librgw2, rbd-nbd, ceph-mib, +17 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenShift AI 2.25 rhoai/odh-dashboard-rhel9 1791853525, rhoai/odh-mod-arch-model-registry-rhel9 1791853432
    fixed: vendor fix RHSA-2026:87410
  • Red Hat OpenShift AI 3.4 rhoai/odh-dashboard-rhel9 1791861020, rhoai/odh-mod-arch-maas-rhel9 1791860708, rhoai/odh-mod-arch-automl-rhel9 1791861032, rhoai/odh-mod-arch-gen-ai-rhel9 1791861479, rhoai/odh-mod-arch-mlflow-rhel9 1791861383, rhoai/odh-mod-arch-autorag-rhel9 1791860994, +2 more
    fixed: vendor fix RHSA-2026:84734
  • Red Hat AMQ Broker 7 amq-broker-bin.zip 7.14.1.CR2, amq-broker-maven-repository.zip 7.14.1.CR2
    not affected: component not present
  • Red Hat OpenShift AI 2.25 rhoai/odh-rhel9-operator 1792570619, rhoai/odh-vllm-cpu-rhel9 1792018436, rhoai/odh-modelmesh-rhel9 1790881700, rhoai/odh-operator-bundle 1792571069, rhoai/odh-vllm-cuda-rhel9 1791358976, rhoai/odh-vllm-rocm-rhel9 1791282503, +64 more Red Hat OpenShift AI 3.4 rhoai/odh-cli-rhel9 1791509689, rhoai/rhai-cli-rhel9 1791509689, rhoai/odh-automl-rhel9 1791535789, rhoai/odh-mlflow-rhel9 1791865967, rhoai/odh-autorag-rhel9 1791557539, rhoai/odh-trainer-rhel9 1791869783, +92 more
    not affected: vulnerable code not present
  • Red Hat OpenShift Container Platform 4 wasmedge, wasmedge-rt, openshift4/ose-console-rhel9
    not affected: vulnerable code not in execute path

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
2mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-09).

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
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
npm @fastify/busboy
>=1.0.0, <3.2.1
3.2.1

Affected products

  • @fastify/busboy @fastify/busboy

Classification

Weakness
  • CWE-754 Improper Check for Unusual or Exceptional Conditions

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.