CVE-2026-19484
@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary
Impact
@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
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @fastify/busboy | >= 3.1.0, < 3.2.1 | 3.2.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Fastify | Fastify\/Busyboy | from 3.1.0 before 3.2.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-xjh9-v7x6-24jw
- https://github.com/fastify/busboy/security/advisories/GHSA-xjh9-v7x6-24jw
- https://nvd.nist.gov/vuln/detail/CVE-2026-19484
- https://github.com/fastify/busboy/commit/632a237e7fb6b3b7a30e0de8fab2ee72ca5bf722
- https://cna.openjsf.org/security-advisories.html
- https://github.com/fastify/busboy/releases/tag/v3.2.1