CVE-2026-19481
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk20th percentile - higher than 20% of all known CVEs
Summary
@fastify/busboy versions 1.0.0 through 3.2.0 are vulnerable to a parser crash by sending a part header whose name is a prototype-inherited property such as __proto__ or constructor. This can trigger a TypeError and potentially terminate the Node.js process, causing an unauthenticated denial of service. The issue is fixed in version 3.2.1.
Risk Assessment
Risk includes Node.js application crashes, potentially leading to service unavailability.
Recommendation
Upgrade @fastify/busboy to version 3.2.1 or later.
Original NVD description (English source)
@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.