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HIGH severity

@fastify/busboy vulnerable to Denial of Service via prototype-named multipart part headerGHSA-x8mw-p69m-v3mx

HIGHFix: fastify/busboy@957a24b

GHSA-x8mw-p69m-v3mx is a high-severity (CVSS 7.5) CWE-754 vulnerability in @fastify/busboy. A fix is available for @fastify/busboy — see the affected versions and patch details below.

Also known asCVE-2026-19481
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-x8mw-p69m-v3mx.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk
0.00%0.33%0.66%0.99%0.3%0.5%0.5%Sep 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-x8mw-p69m-v3mx by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

116other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
@fastify/busboynpm
21.2Mdownloads / week

Description

Impact

Versions of @fastify/busboy from 1.0.0 and prior to 3.2.1 are vulnerable to a Denial of Service. The multipart header parser stores part-header names on a plain JavaScript object, so a part header named __proto__ or constructor resolves to an inherited value that is not an array, and the parser throws TypeError: this.header[h].push is not a function. Through the documented req.pipe(busboy) integration this surfaces as an error event, while direct write()/end() usage throws synchronously and can terminate the Node.js process if uncaught. The parser runs before application middleware, so any unauthenticated client that can submit multipart/form-data is affected.

Patches

Fixed in version 3.2.1.

Workarounds

Attach an error listener to the Busboy stream so the parser failure is handled rather than crashing the process, and wrap direct write()/end() calls in a try/catch. Upgrading to 3.2.1 removes the failure entirely.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npm@fastify/busboy≥ 1.0.0&&< 3.2.13.2.1npm install @fastify/busboy@3.2.1

Affected Products

1 product · 1 configurations
Application
fastify\/busyboyfastify
≥ 1.0.0 && < 3.2.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/busboy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update @fastify/busboy to 3.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x8mw-p69m-v3mx is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This Important flaw affects Red Hat products that use the @fastify/busboy multipart form-data parser, such as OpenShift Container Platform and Red Hat OpenShift AI. An unauthenticated attacker can cause a denial of service by sending crafted form-data headers, leading to the termination of the Node.js process. The…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Source: Red Hat security advisory for GHSA-x8mw-p69m-v3mx (CC BY 4.0)
ProductFixed inAdvisory
Red Hat OpenShift AI 2.25rhoai/odh-dashboard-rhel9:1791853525RHSA-2026:87410
Red Hat OpenShift AI 3.4rhoai/odh-dashboard-rhel9:1791861020RHSA-2026:84734

Frequently Asked Questions

### Impact Versions of `@fastify/busboy` from 1.0.0 and prior to 3.2.1 are vulnerable to a Denial of Service. The multipart header parser stores part-header names on a plain JavaScript object, so a part header named `__proto__` or `constructor` resolves to an inherited value that is not an array, and the parser throws `TypeError: this.header[h].push is not a function`. Through the documented `req.pipe(busboy)` integration this surfaces as an `error` event, while direct `write()`/`end()` usage throws synchronously and can terminate the Node.js process if uncaught. The parser runs before applic
O3 Security · Impact-Aware SCA

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@fastify/busboy vulnerable to Denial of Service via…