CVE-2026-19481
@fastify/busboy vulnerable to Denial of Service via prototype-named multipart part header
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.
INFO
Published Date :
Aug. 13, 2026, 9:17 a.m.
Last Modified :
Sept. 3, 2026, 7:16 p.m.
Remotely Exploit :
No
Source :
ce714d77-add3-4f53-aff5-83d477b104bb
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | ce714d77-add3-4f53-aff5-83d477b104bb |
Solution
- Upgrade @fastify/busboy to version 3.2.1.
- Ensure the header object has a null prototype.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-19481.
| URL | Resource |
|---|---|
| https://cna.openjsf.org/security-advisories.html | Third Party Advisory |
| https://github.com/fastify/busboy/security/advisories/GHSA-x8mw-p69m-v3mx | Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-19481 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-19481
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-19481 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-19481 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 03, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:fastify:fastify/busyboy:*:*:*:*:*:node.js:*:* versions from (including) 1.0.0 up to (excluding) 3.2.1 Added Reference Type openjs: https://cna.openjsf.org/security-advisories.html Types: Third Party Advisory Added Reference Type openjs: https://github.com/fastify/busboy/security/advisories/GHSA-x8mw-p69m-v3mx Types: Mitigation, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 13, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-19481', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-13T14:25:06.775682Z'} -
New CVE Received by ce714d77-add3-4f53-aff5-83d477b104bb
Aug. 13, 2026
Action Type Old Value New Value Added Affected [{'vendor': '@fastify/busboy', 'product': '@fastify/busboy', 'versions': [{'status': 'affected', 'version': '1.0.0', 'lessThan': '3.2.1', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '3.2.1', 'versionType': 'semver'}], 'packageURL': 'pkg:npm/@fastify/busboy', 'defaultStatus': 'unaffected'}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-754 Added Reference https://cna.openjsf.org/security-advisories.html Added Reference https://github.com/fastify/busboy/security/advisories/GHSA-x8mw-p69m-v3mx