Vulnerability · Published Aug 13, 2026 · Assigned by openjs
CVE-2026-19484@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary
High 7.5
In plain English
A high-severity infinite loop in @fastify/busboy from @fastify/busboy. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | @fastify/busboy | 3.2.1 | GHSA-xjh9-v7x6-24jw |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| @fastify/busboy | @fastify/busboy | 3.1.0 – before 3.2.1 |
Weakness: CWE-835, CWE-1322 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H