CVE-2026-19484 PUBLISHED

@fastify/busboy vulnerable to Denial of Service via oversized multipart boundary

Assigner: openjs
Reserved: 10.08.2026 Published: 13.08.2026 Updated: 13.08.2026

@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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Product Status

Vendor @fastify/busboy
Product @fastify/busboy
Versions Default: unaffected
  • affected from 3.1.0 to 3.2.1 (excl.)
  • Version 3.2.1 is unaffected

Credits

  • LorenzoRD2003 reporter
  • mcollina remediation developer
  • UlisesGascon remediation reviewer

References

Problem Types

  • CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') CWE
  • CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context CWE