@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary (CVE-2026-19484) | HOL Guard CVE

High · CVSS 7.5CVE-2026-19484

@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary

Answer in brief

CVE-2026-19484 records a High severity (CVSS 7.5) vulnerability in @fastify/busboy vulnerable to Denial of Service via oversized multipart boundary. The current sources do not mark it as known exploited. The current feed maps @fastify/busboy/@fastify/busboy (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 13, 2026Updated Sep 3, 2026Source checked Sep 27, 2026First seen by HOL Aug 13, 2026Material review Sep 3, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps @fastify/busboy/@fastify/busboy (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:fastify:fastify\/busyboy::::::node.js::*	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
@fastify/busboy/@fastify/busboygeneric	>=3.1.0 <3.2.1	3.2.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for @fastify/busboy/@fastify/busboy.
Review the reported fix. Update @fastify/busboy/@fastify/busboy to 3.2.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 13, 2026

Sources and claim methodology

Upstream source description

@fastify/busboy is a multipart form-data parser. In versions 3.1.0 through 3.2.0, a remote unauthenticated attacker can stall the Node.js event loop by sending a multipart request whose boundary is crafted to a specific length. The vendored streaming search stores its skip table in a fixed 256 entry byte array, and a boundary of exactly 252 bytes makes the search needle 256 bytes, which truncates the default skip distance to zero and turns the search into a CPU bound loop on a small body. A single small request can keep one core busy and deny service to other requests handled by the same process. The issue is fixed in @fastify/busboy 3.2.1, which widens the skip table so the skip distance is preserved. Users should upgrade to 3.2.1.

Quoted source text, attributed separately from HOL analysis.