Vulnerability Description
@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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Fastify | Fastify\/Busyboy | >= 1.0.0, < 3.2.1 |
Related Weaknesses (CWE)
References
- https://cna.openjsf.org/security-advisories.htmlThird Party Advisory
- https://github.com/fastify/busboy/security/advisories/GHSA-x8mw-p69m-v3mxMitigationVendor Advisory
FAQ
What is CVE-2026-19481?
CVE-2026-19481 is a vulnerability with a CVSS score of 7.5 (HIGH). @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...
How severe is CVE-2026-19481?
CVE-2026-19481 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-19481?
Check the references section above for vendor advisories and patch information. Affected products include: Fastify Fastify\/Busyboy.